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
Links
- Eric Weisstein's World of Mathematics, Pyramidal Number
- Index entries for sequences related to binary expansion of n
Programs
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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 *)