A238204 - OEIS

%I #31 May 16 2014 05:55:34

%S 10,16,22,26,28,34,36,40,46,50,52,56,58,64,66,70,76,78,82,86,88,92,94,

%T 96,100,106,112,116,118,120,124,126,130,134,136,142,144,146,154,156,

%U 160,162,166,170,172,176,178,184,186,188,196,202,204,206,210,214,216

%N Even numbers n such that the difference with the preceding prime is prime.

%H Vincenzo Librandi, <a href="/A238204/b238204.txt">Table of n, a(n) for n = 1..1000</a>

%e 28 is in the list because 23 is the greatest prime less than 28 and 28 - 23 = 5 is also prime.

%p a:= proc(n) option remember; local k;

%p       for k from `if`(n=1, 4, a(n-1)+2) by 2

%p       while not isprime(k-prevprime(k)) do od; k

%p     end:

%p seq(a(n), n=1..60);  # _Alois P. Heinz_, Mar 03 2014

%t Select[Range[99] 2, PrimeQ[# - NextPrime[#, -1]] &] (* _Giovanni Resta_, Feb 22 2014 *)

%K nonn

%O 1,1

%A _Franz Vrabec_, Feb 20 2014