A359003 a(n) is the smallest n-gonal number whose sum of digits is n.

3, 4, 5, 6, 7, 8, 9, 370, 506, 156, 238, 671, 726, 88, 836, 585, 775, 7337, 5268, 8149, 8555, 8961, 9367, 9773, 15786, 9856, 91964, 65757, 89428, 179960, 47796, 108979, 197945, 86976, 467974, 998516, 259896, 598792, 1737788, 869649, 969991, 1985984, 998676, 3798496, 7979546, 5877696

Offset

3,1

Links

Table of n, a(n) for n=3..48.

Eric Weisstein's World of Mathematics, Polygonal Number

Example

370 is the smallest 10-gonal number with digit sum 10, so a(10) = 370.

Mathematica

p[n_, k_] := (n - 2)*k*(k - 1)/2 + k; a[n_] := Module[{k = 1, pk}, While[Plus @@ IntegerDigits[pk = p[n, k]] != n, k++]; pk]; Array[a, 45, 3] (* Amiram Eldar, Dec 10 2022 *)

Crossrefs

Cf. A007953, A051885, A062685, A062688, A358930.

Sequence in context: A077528 A392568 A329254 * A183296 A138928 A116587

Adjacent sequences: A359000 A359001 A359002 * A359004 A359005 A359006

Keyword

nonn,base

Author

Ilya Gutkovskiy, Dec 10 2022

Status

approved