A320313 Number of ways to write n as the sum of 4 positive integers a, b, c, d such that d < b and a/b - c/d = (a - c)/(b - d).

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 2, 0, 2, 0, 1, 1, 0, 1, 1, 2, 1, 1, 2, 0, 2, 1, 3, 1, 2, 2, 1, 1, 2, 3, 2, 2, 3, 2, 2, 1, 4, 1, 4, 2, 2, 3, 5, 3, 3, 2, 5, 1, 4, 2, 4, 5, 4, 3, 3, 4, 4, 3, 3, 3, 6, 2, 5, 4, 7, 3, 9, 3, 4, 3, 5

Offset

1,22

Links

Hugo Pfoertner, Table of n, a(n) for n = 1..1000

Prog

(PARI) m=86; v=vector(m); for(a=1, m, for(b=1, m, for(c=1, m, for(d=1, b-1, n=a+b+c+d; if(n<=m, if(a/b-c/d==(a-c)/(b-d), v[n]++)))))); v

Crossrefs

Cf. A026810, A319853, A319854, A320311, A320312.

Sequence in context: A356915 A226786 A266330 * A319227 A219490 A341021

Adjacent sequences: A320310 A320311 A320312 * A320314 A320315 A320316

Keyword

nonn

Author

Hugo Pfoertner, Oct 10 2018

Status

approved