A087031 - OEIS

A087031

Numbers n such that 2p-n is prime, p is the smallest prime > n.

1, 3, 9, 15, 27, 31, 33, 39, 47, 57, 61, 63, 69, 75, 91, 93, 99, 105, 115, 117, 123, 135, 141, 147, 151, 159, 167, 177, 183, 185, 189, 195, 199, 213, 217, 219, 225, 237, 245, 251, 257, 267, 271, 273, 279, 297, 301, 303, 309, 325, 341, 345, 361, 367, 375

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

EXAMPLE

3 is a term because smallest prime >3 is 5 and 2*5-3=7 is prime.

MATHEMATICA

Select[Range[400], PrimeQ[2*NextPrime[#]-#]&] (* Harvey P. Dale, Jul 02 2018 *)

PROG

(PARI) isok(n) = isprime(2*nextprime(n+1) - n); \\ Michel Marcus, Oct 03 2013

CROSSREFS