A126017 - OEIS

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A126017

Smallest prime of the form k^n + k^(n-1) - 1.

2, 5, 11, 23, 47, 971, 191, 383, 22136835839, 1310719, 2259801991, 6143, 353563778431304822783, 91424858111, 5425784582791, 57395627, 21474836479, 1099999999999999999, 786431, 13508517176729920889

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OFFSET

1,1

COMMENTS

Primes arising in A125973.

LINKS

Table of n, a(n) for n=1..20.

EXAMPLE

Consider n = 10. k^n + k^(n-1) - 1 evaluates to 1, 1535, 78731, 1310719 for k = 1, ..., 4. Only the last of these numbers, 4^10+4^9-1 = 1310719, is prime, hence a(10) = 1310719.

PROG

(PARI) {for(n=1, 20, k=1; while(!isprime(a=k^n+k^(n-1)-1), k++); print1(a, ", "))} - Klaus Brockhaus, Dec 17 2006

CROSSREFS

Cf. A000040, A045546, A125881-A125885, A125965-A125973.

Sequence in context: A007505 A246492 A059411 * A292937 A034468 A283075

Adjacent sequences: A126014 A126015 A126016 * A126018 A126019 A126020

KEYWORD

nonn

AUTHOR

Artur Jasinski, Dec 14 2006

EXTENSIONS

Edited and extended by Klaus Brockhaus, Dec 17 2006

STATUS

approved