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 A358828 #5 Dec 03 2022 13:54:02 %S A358828 1,0,1,2,5,8,19,30,68,111,229,380,799,1280,2519,4325,8128,13666,25758, %T A358828 43085,79300,134571,240124,407794,730398,1224821,2152122,3646566, %U A358828 6338691,10657427,18469865,30913539,53108364,88953395,151396452,253098400,429416589 %N A358828 Number of twice-partitions of n with no singletons. %C A358828 A twice-partition of n is a sequence of integer partitions, one of each part of an integer partition of n. %F A358828 G.f.: Product_{k>=1} 1/(1-(A000041(k)-1)*x^k). %e A358828 The a(2) = 1 through a(6) = 19 twice-partitions: %e A358828 (11) (21) (22) (32) (33) %e A358828 (111) (31) (41) (42) %e A358828 (211) (221) (51) %e A358828 (1111) (311) (222) %e A358828 (11)(11) (2111) (321) %e A358828 (11111) (411) %e A358828 (21)(11) (2211) %e A358828 (111)(11) (3111) %e A358828 (21111) %e A358828 (111111) %e A358828 (21)(21) %e A358828 (22)(11) %e A358828 (31)(11) %e A358828 (111)(21) %e A358828 (21)(111) %e A358828 (211)(11) %e A358828 (111)(111) %e A358828 (1111)(11) %e A358828 (11)(11)(11) %t A358828 twiptn[n_]:=Join@@Table[Tuples[IntegerPartitions/@ptn],{ptn,IntegerPartitions[n]}]; %t A358828 Table[Length[Select[twiptn[n],FreeQ[Length/@#,1]&]],{n,0,10}] %Y A358828 The version for multiset partitions of integer partitions is A304966. %Y A358828 Allowing singletons other than (1) gives A358829. %Y A358828 A002865 counts partitions with no 1's. %Y A358828 A063834 counts twice-partitions, strict A296122, row-sums of A321449. %Y A358828 Cf. A000009, A000041, A000219, A001970, A072233, A358824. %K A358828 nonn %O A358828 0,4 %A A358828 _Gus Wiseman_, Dec 03 2022