A365078 - OEIS

%I #12 Sep 27 2023 13:43:08

%S 1,1,1,1,1,5,5,3,13,3,1,7,11,23,7,7,13,17,21,23,47,29,5,55,85,31,21,

%T 31,11,21,23,5,57,21,97,67,11,7,41,43,29,39,11,15,89,21,11,83,47,43,

%U 85,85,17,17,11,127,177,167,15,23,21,17,67,149,113,15,131,47,61,95,53,115,31,79,1

%N a(n) is the least divisor (d) of prime(n)# such that prime(n)# / d + 1 is prime where p# denotes the product of all primes <= p.

%F a(n) = prime(n)# / (A365021(n)-1).

%F Conjecture: a(n) < 2*prime(n).

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

%Y Cf. A002110, A365021.

%K nonn

%O 1,6

%A _Alain Rocchelli_, Aug 20 2023