

A097349


Numbers n such that (Sum (2k)^k, k=1..n) + 1 is prime.


1




OFFSET

1,2


COMMENTS

Some of the larger entries may only correspond to probable primes.
The numbers produced by 72 and 318 have now been certified prime by Primo. 13583, found by PrimeForm using recurrence mode, corresponds to a 60228digit probable prime.  Rick L. Shepherd, Apr 29 2006


LINKS

Table of n, a(n) for n=1..6.


EXAMPLE

13 is a term as 2^1 + 4^2 + 6^3 + 8^4 + 10^5 + 12^6 + 14^7 + 16^8 + 18^9 + 20^10 + 22^11 + 24^12 + 26^13 + 1 = 2518267981703965963, which is prime (certified with Primo).


PROG

(PARI) s=1; for(k=1, 700, s=s+(2*k)^k; if(isprime(s), print1(k, ", ")))


CROSSREFS

Cf. A073825 (Sum k^k, k=1..n, is prime), A097350 ((Sum (2k)^k, k=1..n)  1 is prime).
Sequence in context: A264735 A289926 A188676 * A289790 A109112 A163190
Adjacent sequences: A097346 A097347 A097348 * A097350 A097351 A097352


KEYWORD

more,nonn


AUTHOR

Rick L. Shepherd, Aug 07 2004


EXTENSIONS

One more term from Rick L. Shepherd, Apr 29 2006


STATUS

approved



