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A320312 Number of ways to write n as the sum of 4 positive integers a, b, c, d such that b != d and a/b - c/d = (a - c)/(b - d). 5
0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 0, 1, 2, 1, 2, 1, 0, 5, 1, 3, 1, 3, 3, 2, 2, 3, 4, 4, 3, 5, 1, 4, 4, 8, 3, 6, 4, 4, 4, 6, 6, 7, 5, 8, 5, 6, 4, 11, 4, 11, 6, 7, 6, 13, 8, 7, 8, 13, 4, 11, 5, 12, 10, 11, 9, 11, 9, 10, 10, 12, 7, 18, 6, 15, 10, 15 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,17

LINKS

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

PROG

(PARI) m=80; v=vector(m); for(a=1, m, for(b=1, m, for(c=1, m, for(d=1, m, n=a+b+c+d; if(n<=m, if(b!=d&&a/b-c/d==(a-c)/(b-d), v[n]++)))))); v

CROSSREFS

Cf. A026810, A319853, A319854, A320311, A320313.

Sequence in context: A191312 A240159 A309447 * A269942 A094645 A105793

Adjacent sequences:  A320309 A320310 A320311 * A320313 A320314 A320315

KEYWORD

nonn

AUTHOR

Hugo Pfoertner, Oct 10 2018

STATUS

approved

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Last modified May 11 18:21 EDT 2021. Contains 343808 sequences. (Running on oeis4.)