OFFSET
1,1
FORMULA
a(n) = Sum_{d|n^2} tau((n+d)^2).
EXAMPLE
For n=2 we have 17 solutions (r,u,s,t): (3,6,7,42), (3,6,8,24), (3,6,9,18), (3,6,10,15), (3,6,12,12), (3,6,15,10), (3,6,18,9), (3,6,24,8), (3,6,42,7), (4,4,5,20), (4,4,6,12), (4,4,8,8), (4,4,12,6), (4,4,20,5), (6,3,4,12), (6,3,6,6), (6,3,12,4).
PROG
(PARI) a(n) = sumdiv(n^2, d, numdiv((n+d)^2)) \\ Michel Marcus, Jun 17 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladeta Jovovic, Aug 10 2001
STATUS
approved