A182265 Number of primes p < 10^n such that 4*p+1 is also prime.
2, 9, 31, 176, 1057, 7422, 53709, 407198, 3198946, 25773602, 212205881, 1777532673
Offset: 1
Keywords
Programs
-
Mathematica
f[n_] := Length[Select[Range[10^n], PrimeQ[#] && PrimeQ[4#+1]&]]; Table[f[n], {n,7}] -
PARI
a(n)=my(s=0); forprime(p=2,10^n,s+=isprime(4*p+1));s \\ Charles R Greathouse IV, Apr 23 2012
Extensions
a(10)-a(12) from Charles R Greathouse IV, Apr 23 2012