A094898 - OEIS

%I #15 Jul 21 2021 09:34:03

%S 7,0,0,17,0,0,0,0,0,41,0,0,0,0,0,0,71,0,0,83,0,0,0,0,101,0,0,113,0,0,

%T 0,131,0,0,0,0,0,0,0,0,167,0,0,0,0,0,0,0,197,0,0,0,0,0,0,227,0,233,0,

%U 0,0,0,0,0,0,0,0,0,0,281,0,0,0,0,0,0,311,0,317,0,0,0,0,0,0,0,0,353,0,0,0,0

%N This sequence needs a proper name.

%t a=Table[If[PrimeQ[4*n+1]==True&&PrimeQ[4*n+3]==False, 1, 0], {n, 0, 200}]

%t b=Table[If[PrimeQ[4*n+1]==False&&PrimeQ[4*n+3]==True, 1, 0], {n, 0, 200}]

%t d=Table[If[PrimeQ[a[[n]]*(4*n+1)+b[[n]]*(4*n+3)]==True, a[[n]]*(4*n+1)+b[[n]]*(4*n+3), 0], {n, 1, 200}]

%o (PARI) av(terms) = my(v=[]); for(n=0, oo, if(ispseudoprime(4*n+1) && !ispseudoprime(4*n+3), v=concat(v, [1]), v=concat(v, [0])); if(#v==terms, break)); v

%o bv(terms) = my(v=[]); for(n=0, oo, if(!ispseudoprime(4*n+1) && ispseudoprime(4*n+3), v=concat(v, [1]), v=concat(v, [0])); if(#v==terms, break)); v

%o a(n) = my(avv=av(n), bvv=bv(n), x=avv[#avv], y=bvv[#bvv], val=x*(4*n+1)+y*(4*n+3)); if(ispseudoprime(val), return(val), return(0)) \\ _Felix Fröhlich_, Jul 03 2021; Program adapted from Mathematica code

%Y Cf. A094896, A094897.

%K nonn,uned,obsc,less

%O 1,1

%A _Roger L. Bagula_, Jun 14 2004