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Some curious polygonals

The 44th enneagonal (9-sided polygonal) number is 6666 !
(Sloane's A028992)

The 26th decagonal (10-sided polygonal) number is 2626 !
(Sloane's A001107)

The 74th heptagonal (7-sided polygonal : n[5n-3]) number is 13579
(Sloane's A014637), a number with its odd digits in ascending order !
Variations on the theme :

%N n^2 has digits in ascending order. under A028819
%N Squares with digits in ascending order. under A028820
%N n^2 has digits in descending order. under A028821
%N Squares with digits in descending order. under A028822
%N Primes with digits in ascending order. under A028864
%N Primes with digits in descending order. under A028867
%N Primes that when squared gives numbers with digits in ascending order. under A028865
%N Primes that when squared gives numbers with digits in descending order. under A028868
%N Squares of primes with digits in ascending order. under A028866
%N Squares of primes with digits in descending order. under A028869


A000080 Prime Curios! Prime Puzzle
Wikipedia 80 Le Nombre 80 Numberland 80














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Patrick De Geest - Belgium - Short Bio - Some Pictures
E-mail address : pdg@worldofnumbers.com