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Introduction

Palindromic numbers are numbers which read the same from
left to right (forwards) as from the right to left (backwards)
Here are a few random examples : 7, 3113, 44611644

Hexagonal numbers are defined and calculated by this extraordinary intricate and excruciatingly complex formula.
So, this line is for experts only

base x ( 2 x base - 1 )
The best way to get a 'structural' insight as how to imagine hexagonals is to visit for instance this site :

Normal and Palindromic Hexagonals

So far this compilation counts 61 Palindromic Hexagonals.
Here is the largest one that Feng Yuan discovered on [ January 4, 2008 ]

 This basenumber13.269.591.374.387.166.732.749 has 23 digits yielding the following palindromic hexagonal number 352.164.110.486.420.593.101.030.101.395.024.684.011.461.253 with a length of 45 digits.

All palindromic hexagonal numbers can only end with 1, 3, 5, 6 or 8.

There exist no palindromic hexagonals of length  3, 8, 9, 12, 22, 24, 27, 30, 36, 38, 40.
(Sloane's A082721)

Every hexagonal number is a triangular number.

A good source for such statements is "The Book of Numbers"
by John H. Conway and Richard K. Guy.
Click on the image on the left for more background about the book.
The book can be ordered at 'www.amazon.com'.

Sloane's A046177 gives the first numbers that are both Hexagonal and Square.
1, 1225, 1413721, 1631432881, 1882672131025, ...
Consult also Eric Weisstein's page Hexagonal Square Number.

Sloane's A046180 gives the first numbers that are both Hexagonal and Pentagonal.
1, 40755, 1533776805, 57722156241751, ...
Consult also Eric Weisstein's page Hexagonal Pentagonal Number.

Sloane's A048903 gives the first numbers that are both Hexagonal and Heptagonal.
1, 121771, 12625478965, 1309034909945503, ...
Consult also Eric Weisstein's page Hexagonal Heptagonal Number.

Sloane's A046192 gives the first numbers that are both Hexagonal and Octagonal.
1, 11781, 113123361, 1086210502741, ...
Consult also Eric Weisstein's page Hexagonal Octagonal Number.

Sloane's A048918 gives the first numbers that are both Hexagonal and Nonagonal.
1, 325, 5330229625, 1353857339341, 22184715227362706161, ...
Consult also Eric Weisstein's page Hexagonal Nonagonal Number.

Sources Revealed

 Neil Sloane's "Integer Sequences" Encyclopedia can be consulted online : Neil Sloane's Integer Sequences One can find the regular hexagonal numbers at %N Hexagonal numbers n(2n–1) under A000384. The palindromic hexagonal numbers are categorised as follows : %N n(2n–1) is a hexagonal palindrome under A054970. %N Hexagonal palindromes under A054969. Click here to view some of the author's [P. De Geest] entries to the table. Click here to view some entries to the table about palindromes.

The Table

Index Nr Info BasenumberLength
Palindromic Hexagonal NumberLength

Formula = n(2n–1)
61
T144
Info 13.269.591.374.387.166.732.74923
352.164.110.486.420.593.101.030.101.395.024.684.011.461.25345
60
T143
Info 2.902.825.573.527.004.575.02122
16.852.792.620.644.766.088.388.388.066.744.602.629.725.86144
59
T137
Info 166.735.172.845.051.317.04321
55.601.235.727.338.276.212.021.267.283.372.753.210.65541
58
T136
Info 95.800.231.113.659.236.06120
18.355.368.562.861.046.305.450.364.016.826.586.355.38141
57
T135
Info 17.684.912.039.911.051.42620
625.512.227.718.781.732.353.237.187.817.722.215.52639
56
T133
Info Prime Curios!          9.561.677.372.927.686.36119
182.851.348.367.914.603.505.306.419.763.843.158.28139
55
T130
Info 1.827.172.728.272.717.28219
6.677.120.357.887.130.286.820.317.887.530.217.76637
54
T126
Info 1.666.614.952.453.588.94319
5.555.210.799.483.757.064.607.573.849.970.125.55537
53
T121
Info 967.877.687.832.504.86118
1.873.574.437.207.991.455.541.997.027.344.753.78137
52
T117
Info 123.592.172.047.762.89918
30.550.049.982.967.649.594.676.928.994.005.50335
51
T116
Info 56.270.393.370.816.59217
6.332.714.340.212.879.669.782.120.434.172.33634
50
T115
Info 54.556.973.614.741.45517
5.952.926.739.999.190.550.919.999.376.292.59534
49
T114
Info 54.050.101.714.919.96517
5.842.826.990.786.388.228.836.870.996.282.48534
48
T113
Info 39.179.467.697.750.41917
3.070.061.378.158.136.996.318.518.731.600.70334
47
T112
Info 13.277.954.159.263.74917
352.608.133.311.018.969.810.113.331.806.25333
46
T110
Info 2.250.495.266.170.70116
10.129.457.886.113.466.431.168.875.492.10132
45
T108
Info 1.864.517.945.162.97216
6.952.854.335.669.501.059.665.334.582.59631
44
T107
Info 1.624.954.860.315.51316
5.280.956.596.126.015.106.216.956.590.82531
43
T105
Info 176.760.310.346.46215
62.488.414.627.554.945.572.641.488.42629
42
T104
Info 163.412.656.430.01515
53.407.392.563.028.082.036.529.370.43529
41
T102
Info 82.201.095.219.11114
13.514.040.110.442.624.401.104.041.53129
40
T100
Info 25.182.304.403.14114
1.268.296.910.104.884.010.196.928.62128
39
T96
Info 5.711.952.918.93613
65.252.812.296.277.269.221.825.25626
38
T92
Info 2.031.643.008.98413
8.255.146.631.905.091.366.415.52825
37
T88
Info 208.949.080.21412
87.319.436.244.344.263.491.37823
36
T87
Info 202.635.166.86412
82.122.021.699.799.612.022.12823
35
T85
Info 176.234.896.62612
62.117.477.577.377.577.471.12623
34
T78
Info Prime!          13.347.462.82911
356.309.527.929.725.903.65321
33
T75
Info 8.763.870.45110
153.610.850.555.058.016.35121
32
T72
Info 2.756.800.38710
15.199.896.744.769.899.15120
31
T71
Info 1.783.816.19610
6.364.000.440.440.004.63619
30
T69
Info 1.240.058.21910
3.075.488.771.778.845.70319
29
T68
Info 507.354.4039
514.816.979.979.618.41518
28
T66
Info 184.252.8769
67.898.244.444.289.87617
27
T65
Info 181.737.1829
66.056.806.460.865.06617
26
T64
Info 170.563.6739
58.183.932.923.938.18517
25
T63
Info 91.071.9218
16.588.189.498.188.56117
24
T56
Info 25.004.4418
1.250.444.114.440.52116
23
T51
Info 17.835.1968
636.188.414.881.63615
22
T50
Info 17.352.5868
602.224.464.422.20615
21
T41
Info 5.555.5567
61.728.399.382.71614
20
T39
Info 1.853.9427
6.874.200.024.78613
19
T37
Info 1.620.2137
5.250.178.710.52513
18
T36
Info 810.3116
1.313.207.023.13113
17
T29
Info 83.5275
13.953.435.93111
16
T28
Info 55.5565
6.172.882.71610
15
T27
Info 51.4255
5.289.009.82510
14
T25
Info 25.1415
1.264.114.62110
13
T20
Info 1.6854
5.676.7657
12
T19
Info 1.5934
5.073.7057
11
T17
Info 9173
1.680.8617
10
T16
Info Prime!          7973
1.269.6217
9
T15
Info 6443
828.8286
8
T14
Info 5563
617.7166
7
T13
Info 1823
66.0665
6
T12
Info 872
15.0515
5
T10
Info 552
5.9954
4
T9
Info 392
3.0034
3
T5
Info 61
662
2
T3
Info Prime!          21
61
1
T1
Info 11
11

Contributions

Feng Yuan (email) from Washington State, USA, sent in the palindromic hexagonals
with index number 60 and 61 on [ January 8, 2008 ].

Feng Yuan (email) from Washington State, USA, helped making the list of palindromic hexagonals
starting from index number 1 up to 51.

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