A365021 a(n) is the largest prime of the form P+1 where P divides prime(n)# and p# denotes the product of all primes <= p.

3, 7, 31, 211, 2311, 6007, 102103, 3233231, 17160991, 2156564411, 200560490131, 1060105447831, 27659114866111, 568815710072611, 87841397512641631, 4655594068170006391, 147904642319554818391, 6899316550553351234311, 374205788146679383613291, 24258296962030389607278931

Offset

1,1

Links

Table of n, a(n) for n=1..20.

Formula

Conjecture: a(n) > (1/2) * prime(n-1)#.

Prog

(PARI) a(n) = my(P=vecprod(primes(n)), p=1); while(!ispseudoprime(floor((P/p)+1)) || gcd(P, p)<>p, p=p+2); (P/p)+1;

Crossrefs

Cf. A002110, A006862.

Sequence in context: A343087 A051342 A002585 * A103785 A289127 A289125

Adjacent sequences: A365018 A365019 A365020 * A365022 A365023 A365024

Keyword

nonn

Author

Alain Rocchelli, Aug 16 2023

Status

approved