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 A050343 #16 Dec 19 2015 14:18:57 %S A050343 1,1,1,4,7,14,29,57,110,217,417,794,1513,2860,5373,10063,18740,34750, %T A050343 64221,118199,216775,396297,722136,1311888,2376575,4293407,7735941, %U A050343 13903985,24929763,44595606,79598328,141770576,251984463,446991405,791391545,1398551523 %N A050343 Number of partitions of n into distinct parts with 2 levels of parentheses. %H A050343 Alois P. Heinz, <a href="/A050343/b050343.txt">Table of n, a(n) for n = 0..1000</a> %H A050343 N. J. A. Sloane, <a href="/transforms.txt">Transforms</a> %F A050343 Weigh transform of A050342. %e A050343 4 = ((4)) = ((3))+((1)) = ((3)+(1)) = ((3+1)) = ((2+1))+((1)) = ((2+1)+(1)). %p A050343 g:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0, %p A050343 g(n, i-1)+`if`(i>n, 0, g(n-i, i-1)))) %p A050343 end: %p A050343 h:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0, %p A050343 add(binomial(g(i, i), j)*h(n-i*j, i-1), j=0..n/i))) %p A050343 end: %p A050343 b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0, %p A050343 add(binomial(h(i, i), j)*b(n-i*j, i-1), j=0..n/i))) %p A050343 end: %p A050343 a:= n-> b(n, n): %p A050343 seq(a(n), n=0..50); # _Alois P. Heinz_, May 19 2013 %t A050343 g[n_, i_] := g[n, i] = If[n==0, 1, If[i<1, 0, g[n, i-1] + If[i>n, 0, g[n-i, i-1]]]] ; h[n_, i_] := h[n, i] = If[n==0, 1, If[i<1, 0, Sum[Binomial[g[i, i], j]*h[n-i*j, i-1], {j, 0, n/i}]]]; b[n_, i_] := b[n, i] = If[n==0, 1, If[i<1, 0, Sum[ Binomial[ h[i, i], j]*b[n-i*j, i-1], {j, 0, n/i}]]]; a[n_] := b[n, n]; Table[a[n], {n, 0, 50}] (* _Jean-François Alcover_, Jul 17 2015, after _Alois P. Heinz_ *) %Y A050343 Cf. A050342-A050350. %K A050343 nonn %O A050343 0,4 %A A050343 _Christian G. Bower_, Oct 15 1999