2,1

Jinyuan Wang, Table of n, a(n) for n = 2..2000

a(n) = A000720(A055211(n)) iff A055211(n) is a prime. - Michel Marcus, Oct 05 2019

(PARI) a(n) = {my(k = prod(j=1, n, prime(j))); p = k-precprime(k-2); if(isprime(p), primepi(p), 0); } \\ Jinyuan Wang, Oct 02 2019

Cf. A000720, A055211, A098167.

Sequence in context: A138620 A260820 A248554 * A217445 A007238 A083875

Adjacent sequences: A098163 A098164 A098165 * A098167 A098168 A098169

nonn

Pierre CAMI, Aug 30 2004

Name edited by and more terms from Jinyuan Wang, Oct 02 2019

approved