A220703 Numbers k such that k^7 + 7*k + 7^k is prime.

2, 3, 17, 74, 120, 212, 528, 2348, 13820

Offset

1,1

Links

Table of n, a(n) for n=1..9.

Mathematica

Select[Range[5000], PrimeQ[#^7 + 7*# + 7^#]&]

Prog

(PARI) is(n)=ispseudoprime(n^7+7*n+7^n) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A220528.

Sequence in context: A201455 A085874 A055739 * A342547 A245799 A056794

Adjacent sequences: A220700 A220701 A220702 * A220704 A220705 A220706

Keyword

nonn,more

Author

Vincenzo Librandi, Jan 07 2013

Extensions

a(9) from Michael S. Branicky, Jul 13 2023

Status

approved