A339868 Primes p such that p + A023896(p-1) and p + A023896(p+1) are prime.

2, 7, 29, 61, 83, 109, 293, 311, 449, 709, 773, 997, 1021, 1031, 1103, 1231, 1297, 1301, 1381, 1487, 1523, 1553, 1559, 1709, 2089, 2161, 2221, 2297, 2339, 2377, 2521, 2663, 2677, 2687, 2711, 2927, 3037, 3163, 3167, 3221, 3407, 3533, 4091, 4259, 4729, 5009, 5189, 5309, 5581, 6691, 6899, 7001, 7297

Offset: 1

Author

J. M. Bergot and Robert Israel, Dec 20 2020

Keywords

• nonn

Examples

			a(3) = 29 is a term because 29, 29 + A023896(28) = 197 and 29 + A023896(30) = 149 are prime.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A023896.

Programs

Maple

A023896:= n -> n*numtheory:-phi(n)/2:
A023896(1):= 1:
select(t -> isprime(t+A023896(t-1)) and isprime(t+A023896(t+1)),
[seq(ithprime(i),i=1..1000)]);