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 A344602 #14 May 30 2021 20:56:58 %S A344602 0,1,2,4,7,8,11,13,14,16,19,21,22,25,26,28,32,35,37,38,41,42,44,49,50, %T A344602 52,56,63,64,67,69,70,73,74,76,81,82,84,88,95,97,98,100,104,111,112, %U A344602 119,123,125,126,128,131,133,134,137,138,140,145,146,148,152,159,161 %N A344602 Integers whose Hamming weight is triangular. %H A344602 Alois P. Heinz, <a href="/A344602/b344602.txt">Table of n, a(n) for n = 1..20000</a> %p A344602 q:= n-> issqr(8*add(i, i=Bits[Split](n))+1): %p A344602 select(q, [$0..200])[]; # _Alois P. Heinz_, May 24 2021 %t A344602 Select[Range[0, 200], IntegerQ @ Sqrt[8 * Plus @@ IntegerDigits[#, 2] + 1] &] (* _Amiram Eldar_, May 24 2021 *) %o A344602 (PARI) isok(n) = ispolygonal(hammingweight(n), 3); %Y A344602 Cf. A000120, A000217, A344603. %K A344602 nonn,base %O A344602 1,3 %A A344602 _Michel Marcus_, May 24 2021