A282036 a(n) is the sum of quadratic nonresidues of A002145(n) (the n-th prime == 3 mod 4).

2, 14, 33, 95, 161, 279, 473, 658, 944, 1139, 1491, 1738, 1826, 2884, 2996, 4318, 4585, 5004, 6191, 6683, 7849, 8413, 10314, 10746, 11394, 13157, 13393, 16013, 16566, 18936, 19783, 20376, 23946, 27057, 27804, 30883, 35541, 35232, 36384, 39832, 45671, 50858, 51363, 50059, 55097, 56040

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Christian Aebi, Grant Cairns, Sums of Quadratic residues and nonresidues, arXiv:1512.00896 [math.NT], 2015.

Formula

a(n) = Sum_{k=1..(A002145(n)-1)/2} (-k^2) mod A002145(n). - J. M. Bergot and Robert Israel, Nov 09 2020

Maple

with(numtheory):
a:=[]; m:=[]; d:=[];
for i1 from 1 to 200 do
p:=ithprime(i1);
if (p mod 4) = 3 then
sp:=0; sm:=0;
for j from 1 to p-1 do
if legendre(j, p)=1 then sp:=sp+j; else sm:=sm+j; fi; od;
a:=[op(a), sp]; m:=[op(m), sm]; d:=[op(d), sm-sp];
fi;
od:
a; m; d; # A282035, A282036, A282037
# Alternative:
f:= p -> add(-k^2 mod p, k=1..(p-1)/2)::
map(f, select(isprime, [seq(p, p=3..1000, 4)])); # Robert Israel, Nov 09 2020

Mathematica

f[p_] := Total[Range[p-1] ~Complement~ Table[Mod[k^2, p], {k, (p-1)/2}] ]; f /@ Select[Range[3, 1000, 4], PrimeQ] (* Jean-François Alcover, Feb 16 2018, after Robert Israel *)

Prog

(PARI) lista(nn) = forprime(p=2, nn, if(p%4==3, print1(sum(k=1, p-1, if (!issquare(Mod(k, p)), k)), ", "))); \\ Michel Marcus, Nov 09 2020

Crossrefs

Sums of residues, nonresidues, and their differences, for p == 1 mod 4, p == 3 mod 4, and all p: A171555; A282035, A282036, A282037; A076409, A125615, A282038.

Cf. A002145.

Sequence in context: A322074 A083015 A368628 * A050591 A073535 A225292

Adjacent sequences: A282033 A282034 A282035 * A282037 A282038 A282039

Keyword

nonn

Author

N. J. A. Sloane, Feb 20 2017

Status

approved