OFFSET
1,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..1000
FORMULA
G.f.: Sum(Sum(x^(i+j)*(x^i+x^j-2)/((x^i-1)*(x^j-1)*(x^i+x^j-1)), j=1..i-1), i=2..infinity).
a(n) ~ 1/sqrt(5) * ((1+sqrt(5))/2)^(n+1). - Vaclav Kotesovec, May 01 2014
MAPLE
with(numtheory):
a:= n-> add(add(add(binomial(j+(n-i*j)/d, j), d=select(x->x<i,
divisors(n-i*j))), j=1..n/i), i=2..n-1):
seq(a(n), n=0..50); # Alois P. Heinz, Feb 01 2014
MATHEMATICA
Rest@ CoefficientList[ Series[ Sum[ x^(i + j)*(x^i + x^j - 2)/((x^i - 1)*(x^j - 1)*(x^i + x^j - 1)), {i, 2, 37}, {j, i - 1}], {x, 0, 37}], x] (* Robert G. Wilson v, Sep 16 2007 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Vladeta Jovovic, Sep 13 2007
EXTENSIONS
More terms from Robert G. Wilson v, Sep 16 2007
STATUS
approved