A280555 Primes p such that sigma(sigma(p)) is a Fibonacci number.

19289, 7391381, 9041581, 9124081, 9589141, 645617593711, 786881099503, 793374393583, 188950298985689, 215446003400539, 228846950929339, 257138974382029, 265666386165589, 276918720321829, 280481623844131, 323331286115017, 326905876894417

Offset: 1

Author

Altug Alkan, Jan 05 2017

Keywords

• nonn

Comments

Is this sequence infinite?

Examples

			Prime number 7391381 is a term because sigma(sigma(7391381)) = 14930352 is a Fibonacci number.
		

Crossrefs

Cf. A008333, A051027, A272412, A280545.

Programs

PARI

isFibonacci(n)=my(k=n^2); issquare(k+=(k+1)<<2) || (n>0 && issquare(k-8));
is(n)=isFibonacci(sigma(n+1))&&isprime(n);

Extensions

Terms confirmed by Giovanni Resta, Jan 07 2017