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

Author

Ilya Gutkovskiy, Dec 10 2022

Keywords

• nonn
• base

Examples

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

Links

• Eric Weisstein's World of Mathematics, Polygonal Number

Crossrefs

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

Programs

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 *)