OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
MATHEMATICA
seqQ[n_] := Module[{c1 = 0, c3 = 0}, Do[If[Mod[k, 4] == 1 && PrimeQ[k], c1++]; If[Mod[k, 4] == 3 && PrimeQ[k], c3++], {k, n, 2 n}]; c1 == c3]; Select[Range[250], seqQ] (* Amiram Eldar, Dec 16 2019 *)
npfQ[n_]:=With[{prs=Select[Range[n, 2n], PrimeQ]}, Length[Select[prs, Mod[#, 4]==1&]]==Length[Select[prs, Mod[#, 4]==3&]]]; Select[ Range[ 250], npfQ] (* Harvey P. Dale, Sep 25 2024 *)
PROG
(PARI) for(m=1, 250, my(k1=0, k3=0); forprime(p=m, 2*m, if(p%4==1, k1++); if(p%4==3, k3++)); if(k1==k3, print1(m, " "))) \\ Hugo Pfoertner, Dec 16 2019
(Magma) f:=func<n, r|#[p:p in PrimesInInterval(n, 2*n)| p mod 4 eq r]>; [k:k in [1..250]|f(k, 1) eq f(k, 3)]; // Marius A. Burtea, Dec 16 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Jason Earls, Jul 30 2003
STATUS
approved