A094898 This sequence needs a proper name.

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, 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, 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

Offset: 1

Author

Roger L. Bagula, Jun 14 2004

Keywords

• nonn
• uned
• obsc
• less

Crossrefs

Cf. A094896, A094897.

Programs

Mathematica

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

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
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
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