A341805 Numbers k such that (product of first k primes)-1 is divisible by the (k+1)-th prime.

0, 2, 4, 9823712

Offset

1,2

Links

Table of n, a(n) for n=1..4.

Formula

a(n) = A000720(A341804(n)) - 1.

Example

4 is a member because 2*3*5*7-1 (product of first 4 primes, minus one) is divisible by the 5th prime, 11.
9823712 is a member because 2*3*5*...*176078267-1 is divisible by 176078293, where 176078267 is the 9823712th prime.

Prog

(PARI) isok(k) = ((vecprod(primes(k)) - 1) % prime(k+1)) == 0; \\ Michel Marcus, Mar 03 2021

Crossrefs

Cf. A079276, A081618, A338543, A341804, A341812.

Sequence in context: A079236 A138852 A062701 * A252783 A192225 A020821

Adjacent sequences: A341802 A341803 A341804 * A341806 A341807 A341808

Keyword

nonn,hard,more

Author

Jeppe Stig Nielsen, Feb 20 2021

Status

approved