A119547 10-gonal numbers for which the sum of the digits is also a 10-gonal number.

0, 1, 10, 370, 451, 1540, 3052, 5967, 7965, 15687, 18837, 27972, 36576, 38907, 40501, 43785, 48951, 66177, 72495, 75762, 89550, 93177, 124785, 130501, 137826, 146880, 165852, 170775, 175770, 180837, 191187, 196470, 223965, 229680, 235467, 247257, 259335, 265482

Offset

1,3

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

5967 is a decagonal number whose sum of digits 5+9+6+7 = 27 is also decagonal.

Mathematica

sod[n_] := Plus @@ IntegerDigits[n]; decQ[n_] := n == 0 || IntegerQ[(Sqrt[64*n + 36] + 6)/16]; Select[Table[n*(4*n - 3), {n, 0, 300}], decQ[sod[#]] &] (* Amiram Eldar, Feb 06 2021 *)

Prog

(PARI) isok(n) = ispolygonal(n, 10) && ispolygonal(sumdigits(n), 10); \\ Michel Marcus, Feb 06 2021

Crossrefs

Cf. A001107, A007953.

Sequence in context: A079914 A051790 A220638 * A117797 A301311 A291530

Adjacent sequences: A119544 A119545 A119546 * A119548 A119549 A119550

Keyword

base,nonn

Author

Luc Stevens (lms022(AT)yahoo.com), May 28 2006

Extensions

a(1)=0 and a missing term inserted by Amiram Eldar, Feb 06 2021

Status

approved