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

1,1

Comments

Is this sequence infinite?

Links

Table of n, a(n) for n=1..17.

Example

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

Prog

(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);

Crossrefs

Cf. A008333, A051027, A272412, A280545.

Sequence in context: A186875 A251803 A184667 * A031831 A252901 A126721

Adjacent sequences: A280552 A280553 A280554 * A280556 A280557 A280558

Keyword

nonn

Author

Altug Alkan, Jan 05 2017

Extensions

Terms confirmed by Giovanni Resta, Jan 07 2017

Status

approved