This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A165951 #26 Jun 02 2025 02:05:40
%S A165951 0,0,0,1,1,0,0,1,3,0,3,0,0,1,5,0,3,0,1,7,0,5,3,0,0,0,5,3,0,0,5,5,0,3,
%T A165951 0,7,0,1,11,0,5,0,13,0,0,9,3,7,5,0,0,15,0,7,0,13,0,11,0,0,3,0,3,19,0,
%U A165951 0,3,0,5,0,0,19,9,0,3,17,0,0,0,0,9,0,21,0,15,5,0,0,0,7,7,25,7,9,3,21,0,0
%N A165951 a(n) = (Sum of the quadratic non-residues of prime(n) - Sum of the quadratic residues of prime(n)) / prime(n).
%C A165951 The positive terms are A002143 minus its first term (for p=3, A002143(1)=1 corresponds to 0 here). - _Javier Múgica_, Nov 23 2024
%H A165951 C. H. Gribble, <a href="/A165951/b165951.txt">Table of n, a(n) for n=1,..., 348513 (i.e. for primes < 5x10^6)</a>.
%F A165951 a(n) = Sum_{j=1..prime(n)-1} floor(j^2/prime(n)) - floor((prime(n)-2)*(prime(n)-1)/3) for n >= 3.
%F A165951 a(n) = A125616(n) - A076410(n) for n>=3.
%Y A165951 Cf. A076410, A125616.
%Y A165951 Cf. allso A002143 (positive terms).
%K A165951 nonn
%O A165951 1,9
%A A165951 _Christopher Hunt Gribble_, Oct 01 2009
%E A165951 a(1)-a(2) added by _Christopher Hunt Gribble_, Oct 07 2009