A071782 - OEIS

%I #7 Feb 18 2023 08:08:59

%S 0,1,1,1,0,2,0,5,3,5,0,2,0,0,0,14,0,6,0,15,7,0,0,18,0,13,18,0,0,0,0,8,

%T 0,17,0,24,0,0,13,15,0,14,0,22,0,0,0,28,0,25,0,39,0,9,0,28,19,29,0,30,

%U 0,0,21,32,0,0,0,17,0,0,0,36,0,37,50,38,0,26,0,10

%N Sum of distinct squares in Z_n (mod n).

%C a(n)=0 for prime n>3. - _T. D. Noe_, Sep 06 2005

%H Antti Karttunen, <a href="/A071782/b071782.txt">Table of n, a(n) for n = 1..16848</a>

%t a[n_] := Mod[Apply[Plus, Union[Table[Mod[i^2, n], {i, 1, n}]]], n]

%o (PARI) A071782(n) = (vecsum(Set(vector(n,i,(i^2)%n)))%n); \\ _Antti Karttunen_, Feb 18 2023

%K nonn

%O 1,6

%A _Santi Spadaro_, Jun 24 2002