A359315 a(n) is the smallest centered triangular number with binary weight n.

1, 10, 19, 46, 31, 235, 631, 1786, 1999, 7669, 7039, 12286, 16381, 180094, 114679, 949231, 2086831, 2883574, 4175839, 12480511, 50329585, 62898151, 132638719, 234618814, 771743710, 2883510271, 4269733885, 8254119871, 17045499901, 33214168831

Offset

1,2

Links

Table of n, a(n) for n=1..30.

Eric Weisstein's World of Mathematics, Centered Triangular Number

Index entries for sequences related to binary expansion of n

Example

235 is the smallest centered triangular number with binary weight 6 (235_10 = 11101011_2), so a(6) = 235.

Mathematica

seq[len_, nmax_] := Module[{s = Table[0, {len}], n = 1, c = 0, bw, ct}, While[c < len && n < nmax, bw = DigitCount[ct = 3*n*(n-1)/2 + 1, 2, 1]; If[bw <= len && s[[bw]] == 0, c++; s[[bw]] = ct]; n++]; s]; seq[30, 10^6] (* Amiram Eldar, Dec 26 2022 *)

Crossrefs

Cf. A000120, A005448, A089999, A358932, A359316.

Sequence in context: A245003 A372096 A298487 * A082659 A088409 A219959

Adjacent sequences: A359312 A359313 A359314 * A359316 A359317 A359318

Keyword

nonn,base

Author

Ilya Gutkovskiy, Dec 25 2022

Status

approved