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 A266164 #21 Aug 22 2025 18:02:09 %S A266164 3,5,7,11,17,23,37,41,47,101,137,233,257,857,1297,1601,2017,4337, %T A266164 14401,16097,30497,62801,65537,77617,686737,18800897,255080417, %U A266164 12885295097,12918324737,96052225601,516392008697,7026644072737 %N A266164 Primes p such that phi(p) = phi(p-2) + phi(p-1); Phibonacci primes. %C A266164 Primes from A065557; complement of A065572 with respect to A065557. %C A266164 The first 5 known Fermat primes from A019434 are in sequence. %e A266164 17 is in this sequence because phi(17) = phi(15) + phi(16); 16 = 8 + 8. %p A266164 select(t -> isprime(t) and t-1 = numtheory:-phi(t-1) + numtheory:-phi(t-2), [seq(i,i=3..10^6,2)]); # _Robert Israel_, Dec 22 2015 %t A266164 Select[Prime[Range[56000]],EulerPhi[#]==EulerPhi[#-2]+EulerPhi[#-1]&] (* The program generates the first 26 terms of the sequence. *) (* _Harvey P. Dale_, Aug 22 2025 *) %o A266164 (Magma) [n: n in [3..5*10^7] | IsPrime(n) and EulerPhi(n) eq EulerPhi(n-2)+ EulerPhi(n-1)] %Y A266164 Cf. A000010, A065557, A065572. %K A266164 nonn,changed %O A266164 1,1 %A A266164 _Jaroslav Krizek_, Dec 22 2015