

A305738


Numbers k such that k!*T(k)  1 is prime, where T(k) is the kth triangular number.


1



2, 4, 28, 34, 47, 62, 228, 256, 258, 341, 848, 1362, 1709, 2262, 2692, 7907, 10396, 10501
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OFFSET

1,1


COMMENTS

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


LINKS



MATHEMATICA

Do[If[ PrimeQ[n(n +1)!/2  1], Print@ n], {n, 3000}]


PROG

(PARI) isok(n) = ispseudoprime(n(n+1)!/ 2  1);


CROSSREFS



KEYWORD

nonn,more


AUTHOR



EXTENSIONS



STATUS

approved



