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A227420 Primes p such that p - pi(p) is also prime. 2
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 (list; graph; refs; listen; history; text; internal format)
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, 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

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Last modified September 21 19:59 EDT 2019. Contains 327282 sequences. (Running on oeis4.)