

A231326


Primes p such that p  2*k is also prime, where p is kth prime.


2



17, 19, 23, 37, 47, 67, 71, 73, 83, 89, 97, 113, 131, 137, 139, 149, 151, 157, 167, 179, 181, 197, 199, 223, 233, 263, 307, 331, 353, 379, 397, 419, 421, 439, 443, 457, 461, 463, 503, 557, 587, 613, 631, 641, 643, 659, 661, 677, 701, 719, 743, 761, 773, 839, 863
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OFFSET

1,1


LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..5200


EXAMPLE

a(2)= 19 which is 8th prime. prime(8)2*8= 1916= 3 which is also prime.
a(6)= 67 which is 19th prime. prime(19)2*19= 6738= 29 which is also prime.


MAPLE

KD := proc() local a, b; a:= ithprime(n); b := a2*n; if isprime(b) then RETURN (a); fi; end: seq(KD(), n=1..500);


MATHEMATICA

TK = Select[Table[{Prime[n], Prime[n]  2*n}, {n, 200}], PrimeQ[#[[2]]] &]; Transpose[TK][[1]]


CROSSREFS

Cf. A061068 (primes: prime(m) plus its subscript).
Cf. A064402 (numbers n: prime(n)+n is prime).
Cf. A227420 (primes: p  pi(p) is also prime).
Cf. A231232 (primes: prime(k)+2*k is also prime).
Sequence in context: A144487 A108266 A102325 * A038711 A288613 A154881
Adjacent sequences: A231323 A231324 A231325 * A231327 A231328 A231329


KEYWORD

nonn


AUTHOR

K. D. Bajpai, Nov 07 2013


STATUS

approved



