A358932 a(n) is the smallest centered n-gonal number with binary weight n.

19, 85, 31, 469, 253, 2025, 5995, 4061, 15742, 48061, 8191, 220543, 384766, 3080161, 3272671, 6192631, 8385271, 31453021, 58159102, 249495467, 401469279, 268418041, 134193151, 2885548927, 1610563582, 8589393821, 33280753395, 83751780091, 171658174447

Offset

3,1

Links

Table of n, a(n) for n=3..31.

Eric Weisstein's World of Mathematics, Centered Polygonal Number

Index entries for sequences related to binary expansion of n

Example

31 is the smallest centered pentagonal number with binary weight 5 (31_10 = 11111_2), so a(5) = 31.

Mathematica

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

Crossrefs

Cf. A000120, A358930, A358931.

Sequence in context: A062639 A209369 A288749 * A039609 A063496 A027848

Adjacent sequences: A358929 A358930 A358931 * A358933 A358934 A358935

Keyword

nonn,base

Author

Ilya Gutkovskiy, Dec 06 2022

Status

approved