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A078595
Number of pairs (x,y) 1<=x<=y<=n such that 1/x+1/y+1/n = 1/2.
0
0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 2, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
OFFSET
1,12
FORMULA
It seems that for n>=43 a(n) = 0
PROG
(PARI) a(n)=sum(i=1, n, sum(j=1, i, if(1/i+1/j+1/n-1/2, 0, 1)))
CROSSREFS
Sequence in context: A291749 A370599 A253786 * A301989 A216513 A364419
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Dec 08 2002
STATUS
approved

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Last modified September 24 07:53 EDT 2024. Contains 376188 sequences. (Running on oeis4.)