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 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). 5
 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 (list; graph; refs; listen; history; text; internal format)
 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: A341981 A226786 A266330 * A319227 A219490 A341021 Adjacent sequences:  A320310 A320311 A320312 * A320314 A320315 A320316 KEYWORD nonn AUTHOR Hugo Pfoertner, Oct 10 2018 STATUS approved

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Last modified July 29 17:41 EDT 2021. Contains 346346 sequences. (Running on oeis4.)