A358931 a(n) is the smallest n-gonal pyramidal number with binary weight n.

35, 30, 405, 95, 6860, 765, 28855, 7923, 96760, 380091, 259064, 915915, 3845501, 1436415, 32471830, 11992255, 62904941, 182171613, 266182382, 670936891, 939382515, 2533347310, 30530860911, 1876688877, 16972115903, 201845686175, 529756691451, 409027868651, 2713039388125

Offset

3,1

Links

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

Eric Weisstein's World of Mathematics, Pyramidal Number

Index entries for sequences related to binary expansion of n

Example

405 is the smallest pentagonal pyramidal number with binary weight 5 (405_10 = 110010101_2), so a(5) = 405.

Mathematica

p[n_, k_] := k*(k + 1)*((n - 2)*k + 5 - n)/6; a[n_] := Module[{k = 1, pk}, While[DigitCount[pk = p[n, k], 2, 1] != n, k++]; pk]; Array[a, 30, 3] (* Amiram Eldar, Dec 09 2022 *)

Crossrefs

Cf. A000120, A358930, A358932.

Sequence in context: A174027 A259083 A244214 * A267077 A267394 A022991

Adjacent sequences: A358928 A358929 A358930 * A358932 A358933 A358934

Keyword

nonn,base

Author

Ilya Gutkovskiy, Dec 06 2022

Status

approved