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A231232 Primes p such that p + 2*k is also prime, where p is k-th prime. 10
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..5800

EXAMPLE

a(5)= 31: It is 11th prime, included in sequence because  prime(11)+2*11= 31+22= 53, which is also prime.

a(10)= 89: It is 24th prime, included in sequence because  prime(24)+2*24= 89+48= 137, which is also prime.

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);

MATHEMATICA

t = Select[Table[{Prime[n], Prime[n] + 2*n}, {n, 200}], PrimeQ[#[[2]]] &]; Transpose[t][[1]] (* T. D. Noe, Nov 06 2013 *)

PROG

(PARI) is(n)=isprime(n+2*primepi(n)) && isprime(n) \\ Charles R Greathouse IV, Aug 25 2014

(MAGMA) [NthPrime(n): n in [1..250] | IsPrime(NthPrime(n)+2*n)]; // Vincenzo Librandi, Jan 19 2015

CROSSREFS

Cf. A061068 (primes: prime(m) plus its subscript).

Cf. A064402 (numbers n: prime(n)+n is prime).

Sequence in context: A079017 A211440 A100564 * A154608 A024862 A025106

Adjacent sequences:  A231229 A231230 A231231 * A231233 A231234 A231235

KEYWORD

nonn,easy

AUTHOR

K. D. Bajpai, Nov 06 2013

STATUS

approved

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Last modified May 12 17:11 EDT 2021. Contains 343829 sequences. (Running on oeis4.)