A320792 Number of multisets of exactly seven partitions of positive integers into distinct parts with total sum of parts equal to n.

1, 1, 3, 5, 11, 19, 37, 63, 114, 192, 331, 547, 914, 1482, 2412, 3847, 6126, 9620, 15052, 23292, 35889, 54806, 83294, 125658, 188656, 281418, 417828, 616838, 906516, 1325457, 1929644, 2796189, 4035315, 5798648, 8300214, 11833892, 16810048, 23790327, 33552202

Offset: 7

Author

Alois P. Heinz, Oct 21 2018

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 7..1000

Crossrefs

Column k=7 of A285229.

Cf. A000009.

Programs

Maple

g:= proc(n) option remember; `if`(n=0, 1, add(add(`if`(d::odd,
      d, 0), d=numtheory[divisors](j))*g(n-j), j=1..n)/n)
    end:
b:= proc(n, i) option remember; series(`if`(n=0, 1, `if`(i<1, 0,
      add(b(n-i*j, i-1)*x^j*binomial(g(i)+j-1, j), j=0..n/i))), x, 8)
    end:
a:= n-> coeff(b(n$2), x, 7):
seq(a(n), n=7..60);

Formula

a(n) = [x^n y^7] Product_{j>=1} 1/(1-y*x^j)^A000009(j).