

A231432


Primes p such that abs(p  3*k) is also prime, where p is the kth prime.


1



3, 7, 13, 19, 31, 41, 47, 53, 61, 71, 79, 89, 101, 107, 113, 139, 151, 173, 193, 199, 223, 229, 239, 251, 271, 281, 293, 349, 373, 397, 433, 457, 463, 521, 541, 557, 569, 593, 601, 613, 619, 641, 647, 673, 683, 743, 787, 809, 839, 911, 941, 953, 971, 1013, 1049
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OFFSET

1,1


LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..6400


EXAMPLE

The first prime, 2, is not a term since 23*1 = 1.
The second prime, 3, is a term, since 32*3 = 3 is a prime.
a(11) = 79 which is the 22nd prime, prime(22)3*22 = 7966 = 13 which is also prime.
a(15) = 113 which is the 30th prime, prime(30)3*30 = 11390 = 23 which is also prime.


MAPLE

KD := proc() local a, b; a:= ithprime(n); b:= abs(a3*n); if isprime(b) then RETURN (a); fi; end: seq(KD(), n=1..500);


MATHEMATICA

KD = Select[Table[{Prime[n], Prime[n]  3*n}, {n, 200}], PrimeQ[#[[2]]] &]; Transpose[KD][[1]]


PROG

(PARI) k=0; forprime(p=2, 1e3, if(isprime(abs(pk++*3)), print1(p", "))) \\ Charles R Greathouse IV, Mar 11 2014


CROSSREFS

Cf. A061068 (primes: prime(m) plus its subscript).
Cf. A064402 (numbers n: prime(n)+n is prime).
Cf. A231232 (primes p : p+2*k is also prime).
Cf. A231383 (primes p : p+3*k is also prime).
Sequence in context: A304874 A167473 A256864 * A271981 A103521 A103966
Adjacent sequences: A231429 A231430 A231431 * A231433 A231434 A231435


KEYWORD

nonn,easy


AUTHOR

K. D. Bajpai, Nov 09 2013


STATUS

approved



