A231232 Primes p = prime(k) such that p + 2*k is prime.
3, 5, 17, 23, 31, 37, 41, 43, 61, 89, 103, 107, 109, 113, 151, 163, 191, 193, 241, 251, 257, 269, 281, 307, 311, 313, 317, 359, 373, 409, 433, 463, 487, 557, 563, 593, 601, 607, 643, 647, 691, 701, 761, 787, 811, 823, 857, 863, 907, 911, 953, 977, 1019, 1033
Offset: 1
Examples
31 = prime(11) is a term: prime(11) + 2*11 = 31 + 22 = 53 is also prime. 89 = prime(24) is a term: prime(24) + 2*24 = 89 + 48 = 137 is also prime.
Links
- K. D. Bajpai, Table of n, a(n) for n = 1..5800
Crossrefs
Programs
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Magma
[NthPrime(n): n in [1..250] | IsPrime(NthPrime(n)+2*n)]; // Vincenzo Librandi, Jan 19 2015
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Maple
KD := proc() local a,b; a:= ithprime(n); b:= a+2*n; if isprime(b) then RETURN (a); fi; end: seq(KD(),n=1..500);
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Mathematica
t = Select[Table[{Prime[n], Prime[n] + 2*n}, {n, 200}], PrimeQ[#[[2]]] &]; Transpose[t][[1]] (* T. D. Noe, Nov 06 2013 *) -
PARI
is(n)=isprime(n+2*primepi(n)) && isprime(n) \\ Charles R Greathouse IV, Aug 25 2014
Extensions
Name edited by David A. Corneth, Sep 07 2023