This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A280555 #21 Jan 08 2017 11:41:10 %S A280555 19289,7391381,9041581,9124081,9589141,645617593711,786881099503, %T A280555 793374393583,188950298985689,215446003400539,228846950929339, %U A280555 257138974382029,265666386165589,276918720321829,280481623844131,323331286115017,326905876894417 %N A280555 Primes p such that sigma(sigma(p)) is a Fibonacci number. %C A280555 Is this sequence infinite? %e A280555 Prime number 7391381 is a term because sigma(sigma(7391381)) = 14930352 is a Fibonacci number. %o A280555 (PARI) isFibonacci(n)=my(k=n^2); issquare(k+=(k+1)<<2) || (n>0 && issquare(k-8)); %o A280555 is(n)=isFibonacci(sigma(n+1))&&isprime(n); %Y A280555 Cf. A008333, A051027, A272412, A280545. %K A280555 nonn %O A280555 1,1 %A A280555 _Altug Alkan_, Jan 05 2017 %E A280555 Terms confirmed by _Giovanni Resta_, Jan 07 2017