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 A309255 #14 Jul 25 2023 04:04:39
%S A309255 0,1,1,2,3,4,3,4,7,8,7,8,9,10,7,8,15,16,15,16,17,18,15,16,21,22,19,20,
%T A309255 21,22,15,16,31,32,31,32,33,34,31,32,37,38,35,36,37,38,31,32,45,46,43,
%U A309255 44,45,46,39,40,49,50,43,44,45,46,31,32,63,64,63,64,65,66,63,64,69,70,67,68,69
%N A309255 a(n) = n + 1 - Sum_{k=0..n} (Stirling1(n,k) mod 2).
%C A309255 Number of even entries in n-th row of triangle of Stirling numbers of the first kind (A048994).
%H A309255 Amiram Eldar, <a href="/A309255/b309255.txt">Table of n, a(n) for n = 0..10000</a>
%F A309255 G.f.: 1/(1 - x)^2 - (1 + x) * Product_{k>=0} (1 + 2*x^(2^(k+1))).
%F A309255 a(n) = n + 1 - 2^A000120(floor(n/2)).
%t A309255 Table[n + 1 - Sum[Mod[StirlingS1[n, k], 2], {k, 0, n}], {n, 0, 76}]
%t A309255 nmax = 76; CoefficientList[Series[1/(1 - x)^2 - (1 + x) Product[(1 + 2 x^(2^(k + 1))), {k, 0, Floor[Log[2, nmax]] + 1}], {x, 0, nmax}], x]
%o A309255 (PARI) a(n) = n + 1 - sum(k=0, n, stirling(n, k, 1) % 2); \\ _Michel Marcus_, Jul 19 2019
%o A309255 (PARI) a(n) = n + 1 - 2^hammingweight(n\2); \\ _Amiram Eldar_, Jul 25 2023
%Y A309255 Cf. A000120, A048967, A048994, A060632, A309256.
%K A309255 nonn
%O A309255 0,4
%A A309255 _Ilya Gutkovskiy_, Jul 19 2019