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 A087177 #12 Feb 16 2025 08:32:51 %S A087177 0,0,1,1,1,1,1,1,2,3,4,5,5,5,5,6,6,6,6,7,7,8,9,9,9,10,11,12,13,13,14, %T A087177 15,15,15,16,16,16,16,16,16,17,17,18,18,18,19,20,21,21,21,22,22,22,22, %U A087177 22,23,23,24,25,26,26,26,27,27,28,29,30,30,30,30,31,31,31,31,32,33,33 %N A087177 Number of even partition numbers <= P(n), where P=A000041. %H A087177 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PartitionFunction.html">Partition Function</a> %H A087177 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PartitionFunctionPCongruences.html">Partition Function P Congruences</a> %F A087177 a(n) = n + 1 - A071754(n). %o A087177 (PARI) a(n) = sum(k=1, n, !(numbpart(k) % 2)); \\ _Michel Marcus_, Feb 24 2023 %Y A087177 Cf. A000041, A052001, A040051, A071754. %K A087177 nonn %O A087177 0,9 %A A087177 _Reinhard Zumkeller_, Aug 23 2003