This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A359315 #9 Feb 16 2025 08:34:04
%S A359315 1,10,19,46,31,235,631,1786,1999,7669,7039,12286,16381,180094,114679,
%T A359315 949231,2086831,2883574,4175839,12480511,50329585,62898151,132638719,
%U A359315 234618814,771743710,2883510271,4269733885,8254119871,17045499901,33214168831
%N A359315 a(n) is the smallest centered triangular number with binary weight n.
%H A359315 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CenteredTriangularNumber.html">Centered Triangular Number</a>
%H A359315 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a>
%e A359315 235 is the smallest centered triangular number with binary weight 6 (235_10 = 11101011_2), so a(6) = 235.
%t A359315 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 *)
%Y A359315 Cf. A000120, A005448, A089999, A358932, A359316.
%K A359315 nonn,base
%O A359315 1,2
%A A359315 _Ilya Gutkovskiy_, Dec 25 2022