A359093 a(n) is the index of the smallest n-gonal number whose sum of digits is n.
2, 2, 2, 2, 2, 2, 2, 10, 11, 6, 7, 11, 11, 4, 11, 9, 10, 29, 24, 29, 29, 29, 29, 29, 36, 28, 83, 69, 79, 110, 56, 83, 110, 72, 164, 236, 119, 178, 299, 209, 218, 308, 216, 416, 596, 506, 277, 443, 579, 589, 1172, 1217, 991, 1676, 1779, 2315, 1325, 1659, 3125, 2576
Offset: 3
Links
- Harvey P. Dale, Table of n, a(n) for n = 3..100
- Eric Weisstein's World of Mathematics, Polygonal Number
Programs
-
Mathematica
p[n_, k_] := (n - 2)*k*(k - 1)/2 + k; a[n_] := Module[{k = 1}, While[Plus @@ IntegerDigits[p[n, k]] != n, k++]; k]; Array[a, 60, 3] (* Amiram Eldar, Dec 16 2022 *) Table[Module[{k=1},While[Total[IntegerDigits[PolygonalNumber[n,k]]]!=n,k++];k],{n,3,70}] (* Harvey P. Dale, Dec 27 2024 *)