A238445 Primes p such that f(f(p)) is prime, where f(x) = x^5-x^4-x^3-x^2-x-1.

3, 13, 61, 103, 193, 199, 307, 431, 569, 977, 1201, 1451, 1481, 1609, 1669, 1889, 2371, 2381, 2711, 2819, 3083, 3469, 4289, 4337, 4567, 5231, 5501, 6733, 7043, 7253, 7351, 7549, 8707, 9257, 9497, 10039, 10687, 11491, 12227, 12517, 12941, 13397

Offset

1,1

Links

Table of n, a(n) for n=1..42.

Example

3 is prime. 3^5-3^4-3^3-3^2-3-1 = 122 and 122^5-122^4-122^3-122^2-122-1 = 26803717321 is a prime number. Thus, 3 is a member of this sequence.

Prog

(Python)
import sympy
from sympy import isprime, primerange
def f(x):
    return x**5-x**4-x**3-x**2-x-1
[p for p in primerange(2, 10**5) if isprime(f(f(p)))]

Crossrefs

Cf. A125083, A237640.

Sequence in context: A112731 A106884 A232611 * A355298 A328704 A341077

Adjacent sequences: A238442 A238443 A238444 * A238446 A238447 A238448

Keyword

nonn

Author

Derek Orr, Feb 26 2014

Status

approved