A227420 Primes p such that p - pi(p) is also prime.
5, 7, 13, 19, 29, 43, 53, 61, 107, 113, 181, 193, 229, 251, 317, 337, 383, 433, 463, 491, 601, 827, 857, 887, 997, 1033, 1061, 1163, 1193, 1307, 1373, 1531, 1693, 1699, 1721, 1789, 1811, 1831, 1931, 2003, 2029, 2267, 2339, 2347, 2383, 2411, 2423, 2531, 2579, 2617
Offset: 1
Keywords
Links
- Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
Programs
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Maple
5 = A000040(3) and 5 - 3 = 2 prime, 43 = A000040(14) and 43 - 14 = 29 prime.
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Mathematica
fQ[p_] := PrimeQ[p - PrimePi[p]]; Select[ Prime@ Range@ 400, fQ] (* Robert G. Wilson v, Dec 19 2014 *)
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PARI
is(n)=isprime(n) && isprime(n-primepi(n)) \\ Charles R Greathouse IV, Sep 16 2013
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PARI
v=primes(10^4); for(i=1,#v,if(isprime(v[i]-i),print1(v[i]", "))) \\ Charles R Greathouse IV, Sep 16 2013
Comments