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

1,1

Comments

Note that pi(p) are all even, except for the first term. Differs from A101324.

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Maple

5 = A000040(3) and 5 - 3 = 2 prime, 43 = A000040(14) and 43 - 14 = 29 prime.

Mathematica

fQ[p_] := PrimeQ[p - PrimePi[p]]; Select[ Prime@ Range@ 400, fQ] (* Robert G. Wilson v, Dec 19 2014 *)

Prog

(PARI) is(n)=isprime(n) && isprime(n-primepi(n)) \\ Charles R Greathouse IV, Sep 16 2013
(PARI) v=primes(10^4); for(i=1, #v, if(isprime(v[i]-i), print1(v[i]", "))) \\ Charles R Greathouse IV, Sep 16 2013

Crossrefs

Cf. A000040, A000720, A061067, A101324.

Sequence in context: A191046 A045443 A153116 * A099349 A167464 A280266

Adjacent sequences: A227417 A227418 A227419 * A227421 A227422 A227423

Keyword

nonn

Author

Zak Seidov, Sep 16 2013

Status

approved