A116887 Primes p that remain prime through at least 3 iterations of function f(p)=p^2+4.

5087, 11173, 16657, 47017, 54503, 185243, 207643, 300413, 306167, 341813, 391387, 849047, 1348577, 1438223, 1502923, 1857407, 1909267, 2121737, 2161163, 2288773, 2610133, 2725157, 2744723, 2779097, 2874463, 2881327

Offset

1,1

Links

Zak Seidov, Table of n, a(n) for n = 1..2568 All terms up to 10^10.

Example

p=5087, f(p)= 25877573, f(f(p))= 669648784370333 and f(f(f(p)))= 448429494408664742387290530893 are all primes.

Mathematica

Select[Prime[Range[8! ]], PrimeQ[ #^2+4]&&PrimeQ[(#^2+4)^2+4]&&PrimeQ[ ((#^2+4)^2+4)^2+4]&] [Vladimir Joseph Stephan Orlovsky, Feb 26 2010]

Crossrefs

Cf. A062324, A116886, A116888, A116889.

Sequence in context: A209782 A058908 A271171 * A034286 A260069 A252143

Adjacent sequences: A116884 A116885 A116886 * A116888 A116889 A116890

Keyword

nonn

Author

Giovanni Resta, Feb 27 2006

Status

approved