OFFSET
9,5
LINKS
Alois P. Heinz, Table of n, a(n) for n = 9..1000
FORMULA
G.f.: Sum_{i>0} x^(2*i+9) / Product_{j=1..9+i} (1-x^j).
EXAMPLE
a(11) = 1: [10,1].
a(12) = 1: [10,1,1].
a(13) = 3: [10,1,1,1], [10,2,1], [11,2].
a(14) = 4: [10,1,1,1,1], [10,2,1,1], [10,3,1], [11,2,1].
a(15) = 8: [10,1,1,1,1,1], [10,2,1,1,1], [10,2,2,1], [10,3,1,1], [10,4,1], [11,2,1,1], [11,2,2], [12,3].
MAPLE
b:= proc(n, i) option remember;
`if`(n=0 or i=1, 1, b(n, i-1)+`if`(i>n, 0, b(n-i, i)))
end:
a:= n-> add(b(n-2*m-9, min(n-2*m-9, m+9)), m=1..(n-9)/2):
seq(a(n), n=9..60);
MATHEMATICA
b[n_, i_] := b[n, i] = If[n == 0 || i == 1, 1, b[n, i - 1] + If[i > n, 0, b[n - i, i]]];
a[n_] := Sum[b[n - 2 m - 9, Min[n - 2 m - 9, m + 9]], {m, 1, (n - 9)/2}];
a /@ Range[9, 60] (* Jean-François Alcover, Dec 07 2020, after Alois P. Heinz *)
Table[Count[IntegerPartitions[n], _?(MemberQ[#, #[[1]]-9]&)], {n, 9, 60}] (* Harvey P. Dale, Jun 08 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, May 20 2012
STATUS
approved