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A182265 Number of primes p < 10^n such that 4*p+1 is also prime. 4
2, 9, 31, 176, 1057, 7422, 53709, 407198, 3198946, 25773602, 212205881, 1777532673 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..12.

MATHEMATICA

f[n_] := Length[Select[Range[10^n], PrimeQ[#] && PrimeQ[4#+1]&]]; Table[f[n], {n, 7}]

PROG

(PARI) a(n)=my(s=0); forprime(p=2, 10^n, s+=isprime(4*p+1)); s \\ Charles R Greathouse IV, Apr 23 2012

CROSSREFS

Cf. A023212, A092816.

Sequence in context: A150911 A150912 A165653 * A212873 A109770 A242512

Adjacent sequences: A182262 A182263 A182264 * A182266 A182267 A182268

KEYWORD

nonn

AUTHOR

Enrique Pérez Herrero, Apr 22 2012

EXTENSIONS

a(10)-a(12) from Charles R Greathouse IV, Apr 23 2012

STATUS

approved

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Last modified February 2 19:12 EST 2023. Contains 360024 sequences. (Running on oeis4.)