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A097350
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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
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1,1
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COMMENTS
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Some of the larger entries may only correspond to probable primes.
Term 49 corresponds to a certified prime (Primo 2.2.0 beta). Next term is greater than 5400. - Ryan Propper (rpropper(AT)stanford.edu), Aug 23 2005
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LINKS
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Table of n, a(n) for n=1..4.
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EXAMPLE
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6 is a term as 2^1 + 4^2 + 6^3 + 8^4 + 10^5 + 12^6 - 1 = 3090313, which is prime.
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PROG
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(PARI) s=-1; for(k=1, 830, s=s+(2*k)^k; if(isprime(s), print1(k, ", ")))
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CROSSREFS
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Cf. A073825 (Sum k^k, k=1..n, is prime), A097349 ((Sum (2k)^k, k=1..n) + 1 is prime).
Sequence in context: A049383 A099411 A018372 * A062309 A018390 A180615
Adjacent sequences: A097347 A097348 A097349 * A097351 A097352 A097353
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KEYWORD
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nonn
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AUTHOR
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Rick L. Shepherd, Aug 07 2004
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STATUS
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approved
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