OFFSET
1,1
LINKS
Jud McCranie, Table of n, a(n) for n = 1..644
EXAMPLE
1/1 = 1/2 + 1/3 + 1/7 + 1/42
= 1/2 + 1/3 + 1/8 + 1/24
= 1/2 + 1/3 + 1/9 + 1/18
= 1/2 + 1/3 + 1/10 + 1/15
= 1/2 + 1/4 + 1/5 + 1/20
= 1/2 + 1/4 + 1/6 + 1/12
so a(1) = 6.
MATHEMATICA
a[n_] := Length@ Solve[1/n == 1/w + 1/x + 1/y + 1/z && 0 < w < x < y < z, {w, x, y, z}, Integers]; Array[f, 21]
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Apr 30 2014
STATUS
approved