OFFSET
1,4
COMMENTS
Also number of partitions of n such that the greatest part is not divisible by the number of parts. Equivalence can be shown using Ferrers-Young diagrams.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..500
EXAMPLE
The number of parts is not divisible by the greatest part:
a(5) = 4: [1,2,2], [2,3], [1,4], [5];
a(6) = 8: [1,1,1,1,2], [2,2,2], [1,1,1,3], [3,3], [1,1,4], [2,4], [1,5], [6].
The greatest part is not divisible by the number of parts:
a(5) = 4: [1,1,1,1,1], [1,1,1,2], [1,2,2], [2,3];
a(6) = 8: [1,1,1,1,1,1], [1,1,1,1,2], [1,1,2,2], [2,2,2], [1,1,1,3], [3,3], [1,1,4], [1,5].
MAPLE
b:= proc(n, j, t) option remember;
add(b(n-i, i, t+1), i=j..iquo(n, 2))+
`if`(irem(t, n)>0, 1, 0)
end:
a:= n-> b(n, 1, 1):
seq(a(n), n=1..50);
MATHEMATICA
b[n_, j_, t_] := b[n, j, t] = Sum[b[n-i, i, t+1], {i, j, Quotient[n, 2]}] + If[Mod[t, n]>0, 1, 0]; a[n_] := b[n, 1, 1]; Table[a[n], {n, 1, 50}] (* Jean-François Alcover, Feb 05 2017, translated from Maple *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Nov 21 2011
STATUS
approved