A220703 - OEIS

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A220703

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

1

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

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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

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