A359092 a(n) is the index of the smallest n-gonal pyramidal number with binary weight n.

5, 4, 9, 5, 20, 9, 29, 18, 40, 61, 52, 77, 121, 85, 235, 165, 281, 393, 438, 586, 645, 884, 1997, 777, 1597, 3598, 4901, 4442, 8249, 4582, 10685, 5362, 28473, 23140, 41305, 41266, 67947, 82953, 101229, 151121, 236221, 257326, 385090, 254725, 713021, 669890

Offset

3,1

Links

Table of n, a(n) for n=3..48.

Eric Weisstein's World of Mathematics, Pyramidal Number

Index entries for sequences related to binary expansion of n

Mathematica

p[n_, k_] := k*(k + 1)*((n - 2)*k + 5 - n)/6; a[n_] := Module[{k = 1}, While[DigitCount[p[n, k], 2, 1] != n, k++]; k]; Array[a, 40, 3] (* Amiram Eldar, Dec 17 2022 *)

Crossrefs

Cf. A000120, A358931, A359091.

Sequence in context: A198609 A332794 A054508 * A110617 A371859 A234356

Adjacent sequences: A359089 A359090 A359091 * A359093 A359094 A359095

Keyword

nonn,base

Author

Ilya Gutkovskiy, Dec 16 2022

Status

approved