A369704 Number of pairs (p,q) of partitions of n such that the set of parts in q is a subset of the set of parts in p.
1, 1, 2, 4, 8, 13, 28, 43, 84, 137, 243, 372, 684, 1010, 1702, 2620, 4256, 6276, 10134, 14740, 23094, 33742, 51139, 73550, 111303, 158140, 233006, 331099, 481324, 674778, 973928, 1353504, 1925734, 2668263, 3748636, 5153887, 7201684, 9820055, 13572468, 18445878
Offset: 0
Keywords
Examples
a(5) = 13: (11111, 11111), (2111, 11111), (2111, 2111), (2111, 221), (221, 11111), (221, 2111), (221, 221), (311, 11111), (311, 311), (32, 32), (41, 11111), (41, 41), (5, 5).
Links
- Alois P. Heinz, Table of n, a(n) for n = 0..350
Programs
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Maple
b:= proc(n, m, i) option remember; `if`(n=0, `if`(m=0, 1, 0), `if`(i<1, 0, b(n, m, i-1)+add( add(b(n-i*j, m-i*h, i-1), h=0..m/i), j=1..n/i))) end: a:= n-> b(n$3): seq(a(n), n=0..42);
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Mathematica
b[n_, m_, i_] := b[n, m, i] = If[n == 0, If[m == 0, 1, 0], If[i < 1, 0, b[n, m, i - 1] + Sum[Sum[b[n - i*j, m - i*h, i - 1], {h, 0, m/i}], { j, 1, n/i}]]]; a[n_] := b[n, n, n]; Table[a[n], {n, 0, 42}] (* Jean-François Alcover, Feb 29 2024, after Alois P. Heinz *)