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A097349
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Numbers n such that (Sum (2k)^k, k=1..n) + 1 is prime.
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1
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OFFSET
| 1,2
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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 60228-digit probable prime. - Rick L. Shepherd (rshepherd2(AT)hotmail.com), Apr 29 2006
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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).
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PROG
| (PARI) s=1; for(k=1, 700, s=s+(2*k)^k; if(isprime(s), print1(k, ", ")))
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CROSSREFS
| Cf. A073825 (Sum k^k, k=1..n, is prime), A097350 ((Sum (2k)^k, k=1..n) - 1 is prime).
Sequence in context: A136780 A128743 A188676 * A109112 A163190 A004027
Adjacent sequences: A097346 A097347 A097348 * A097350 A097351 A097352
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KEYWORD
| more,nonn
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AUTHOR
| Rick L. Shepherd (rshepherd2(AT)hotmail.com), Aug 07 2004
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EXTENSIONS
| One more term from Rick L. Shepherd (rshepherd2(AT)hotmail.com), Apr 29 2006
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