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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

%I

%S 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,

%T 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,

%U 3,3,4,4,3,3,3,6,2,5,4,7,3,9,3,4,3,5

%N 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).

%H Hugo Pfoertner, <a href="/A320313/b320313.txt">Table of n, a(n) for n = 1..1000</a>

%o (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

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

%K nonn

%O 1,22

%A _Hugo Pfoertner_, Oct 10 2018

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Last modified September 18 19:05 EDT 2021. Contains 347534 sequences. (Running on oeis4.)