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A305738
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Numbers k such that k!*T(k) - 1 is prime, where T(k) is the k-th triangular number.
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1
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2, 4, 28, 34, 47, 62, 228, 256, 258, 341, 848, 1362, 1709, 2262, 2692, 7907, 10396, 10501
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OFFSET
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1,1
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COMMENTS
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The PFGW program has been used to certify all the terms up to a(18), using a deterministic test which exploits the factorization of a(n) + 1. - Giovanni Resta, Jun 24 2018
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LINKS
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Table of n, a(n) for n=1..18.
Maheswara Rao Valluri, Primes of the form p = 1 + n! Sum n, for some n ∈ N*, arXiv:1803.11461 [math.GM], 2018.
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MATHEMATICA
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Do[If[ PrimeQ[n(n +1)!/2 - 1], Print@ n], {n, 3000}]
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PROG
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(PARI) isok(n) = ispseudoprime(n(n+1)!/ 2 - 1);
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CROSSREFS
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Cf. A302859, A301373.
Sequence in context: A059719 A264930 A226347 * A323447 A227303 A066228
Adjacent sequences: A305735 A305736 A305737 * A305739 A305740 A305741
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KEYWORD
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nonn,more
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AUTHOR
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Maheswara Rao Valluri, Jun 22 2018
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EXTENSIONS
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a(16)-a(18) from Giovanni Resta, Jun 24 2018
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STATUS
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approved
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