The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A186709 Number of quadratic residues (mod p) in the interval [2k+2,4k+2], for primes p=4k+3. 1

%I

%S 0,1,1,3,4,6,9,9,10,15,14,17,16,23,22,29,25,30,34,39,36,37,41,45,48,

%T 52,49,52,52,59,62,66,72,68,78,79,80,87,90,87

%N Number of quadratic residues (mod p) in the interval [2k+2,4k+2], for primes p=4k+3.

%F a(n) = A104635(n) - A186708(n) = A186708(n) - A178154(n) = (A104635(n) - A178154(n))/2 = (A002145(n) - 2*A178154(n) -1)/4.

%o (PARI) forprime( p=1, 399, p%4==3|next; u=3; c=[1, 0]; for(i=2, p-2, bittest(u, i^2%p) & next; u+=1<<(i^2%p); c[i^2%p*2\p+1]++); print1(c[2]", "))

%Y Cf. A002145, A186708, A178154.

%K nonn

%O 1,4

%A _M. F. Hasler_, Feb 25 2011

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 14 16:19 EDT 2021. Contains 345037 sequences. (Running on oeis4.)