A358930 a(n) is the smallest n-gonal number with binary weight n.

21, 169, 117, 190, 1404, 9976, 3961, 11935, 19966, 113401, 98155, 208879, 261501, 3338221, 916475, 3100671, 9943039, 31457140, 50322871, 100523871, 264240373, 2113871829, 2012739435, 532673535, 7415513007, 33017544153, 17112759966, 50983861215, 59039022015

Offset: 3

Author

Ilya Gutkovskiy, Dec 06 2022

Keywords

• nonn
• base

Examples

			117 is the smallest pentagonal number with binary weight 5 (117_10 = 1110101_2), so a(5) = 117.
		

Links

• Eric Weisstein's World of Mathematics, Polygonal Number
• Index entries for sequences related to binary expansion of n

Crossrefs

Cf. A000120, A089998, A089999, A358931, A358932.

Programs

Mathematica

p[n_, k_] := (n - 2)*k*(k - 1)/2 + k; a[n_] := Module[{k = 1, pk}, While[DigitCount[pk = p[n, k], 2, 1] != n, k++]; pk]; Array[a, 25, 3] (* Amiram Eldar, Dec 09 2022 *)