%I A032801
%S A032801 0,0,0,0,1,3,5,9,14,22,30,42,55,73,91,115,140,172,204,244,
%T A032801 285,335,385,445,506,578,650,734,819,917,1015,1127,1240,
%U A032801 1368,1496,1640,1785,1947,2109,2289,2470,2670,2870,3090
%N A032801 Number of unordered sets a,b,c,d of distinct integers from 1..n such 
               that a+b+c+d=0 (mod n).
%D A032801 Barnes, Acta Arith., 5 (1958), p. 65.
%D A032801 E. V. McLaughlin, Numbers of factorizations in non-unique factorial domains, 
               Senior Thesis, Allegeny College, Meadville, PA, April 2004.
%p A032801 f := n-> if n mod 2 <> 0 then (n-1)*(n-2)*(n-3)/24 elif n mod 4 = 0 then 
               (n-4)*(n^2-2*n+6)/24 else (n-2)*(n^2-4*n+6)/24; fi;
%Y A032801 Sequence in context: A081946 A166709 A053618 this_sequence A033818 A120452 
               A144116
%Y A032801 Adjacent sequences: A032798 A032799 A032800 this_sequence A032802 A032803 
               A032804
%K A032801 nonn
%O A032801 0,6
%A A032801 N. J. A. Sloane (njas(AT)research.att.com).