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A025431
Number of partitions of n into 7 nonzero squares.
18
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 3, 1, 2, 3, 1, 1, 4, 2, 3, 4, 1, 4, 3, 1, 5, 4, 3, 4, 4, 4, 3, 4, 4, 5, 7, 3, 5, 7, 3, 5, 8, 4, 7, 7, 4, 8, 6, 3, 9, 10, 6, 8, 8, 7, 7, 8, 8, 9, 11, 7, 9, 12, 6, 8, 15, 8, 12, 12, 7, 15, 10, 8, 16, 13, 11, 13, 13, 12, 11
OFFSET
0,23
FORMULA
a(n) = [x^n y^7] Product_{k>=1} 1/(1 - y*x^(k^2)). - Ilya Gutkovskiy, Apr 19 2019
a(n) = Sum_{o=1..floor(n/7)} Sum_{m=o..floor((n-o)/6)} Sum_{l=m..floor((n-m-o)/5)} Sum_{k=l..floor((n-l-m-o)/4)} Sum_{j=k..floor((n-k-l-m-o)/3)} Sum_{i=j..floor((n-j-k-l-m-o)/2)} A010052(i) * A010052(j) * A010052(k) * A010052(l) * A010052(m) * A010052(o) A010052(n-i-j-k-l-m-o). - Wesley Ivan Hurt, Apr 19 2019
MAPLE
b:= proc(n, i, t) option remember; `if`(n=0, `if`(t=0, 1, 0),
`if`(i<1 or t<1, 0, b(n, i-1, t)+
`if`(i^2>n, 0, b(n-i^2, i, t-1))))
end:
a:= n-> b(n, isqrt(n), 7):
seq(a(n), n=0..120); # Alois P. Heinz, May 30 2014
MATHEMATICA
b[n_, i_, t_] := b[n, i, t] = If[n == 0, If[t == 0, 1, 0], If[i < 1 || t < 1, 0, b[n, i - 1, t] + If[i^2 > n, 0, b[n - i^2, i, t - 1]]]];
a[n_] := b[n, Sqrt[n] // Floor, 7];
Table[a[n], {n, 0, 120}] (* Jean-François Alcover, Apr 30 2018, after Alois P. Heinz *)
CROSSREFS
Column k=7 of A243148.
Sequence in context: A340101 A049847 A255274 * A161070 A161109 A161044
KEYWORD
nonn,look
STATUS
approved