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 A087180 #16 May 22 2025 09:10:47
%S A087180 0,0,0,1,1,1,1,2,2,3,4,4,4,4,5,5,6,7,7,7,8,9,10,10,11,11,12,12,12,12,
%T A087180 13,13,14,15,15,16,16,16,16,17,18,19,19,20,20,20,21,21,22,22,22,23,24,
%U A087180 25,25,25,25,26,26,26,26,27,27,28,28,28,28,28,29,29,30,31,31,31,31,32
%N A087180 Number partition numbers <= P(n) of the form 3*k (P = A000041).
%H A087180 Amiram Eldar, <a href="/A087180/b087180.txt">Table of n, a(n) for n = 0..10000</a>
%H A087180 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PartitionFunction.html">Partition Function</a>.
%H A087180 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PartitionFunctionPCongruences.html">Partition Function P Congruences</a>.
%F A087180 a(n) + A087181(n) + A087182(n) = n + 1.
%t A087180 Accumulate[Table[Boole[Mod[PartitionsP[n], 3] == 0], {n, 0, 100}]] (* _Amiram Eldar_, May 22 2025 *)
%Y A087180 Cf. A000041, A068907, A071754, A087177, A087181, A087182, A087183.
%K A087180 nonn
%O A087180 0,8
%A A087180 _Reinhard Zumkeller_, Aug 23 2003