OFFSET
1,3
COMMENTS
Comment from Max Alekseyev, Nov 22 2009: For a prime p==3 (mod 4), a(p) = p*h(-p) + p*(p-1)/2 where h(-p) is the class number (listed in A002143). For example, h(-19)=1 and a(19) = 19*1 + 19*18/2 = 190.
MATHEMATICA
Table[Sum[Mod[k (n-k), n], {k, n}], {n, 100}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Wouter Meeussen, Sep 06 2009
STATUS
approved