OFFSET
3,1
EXAMPLE
For n=3, primorial(3)=A002110(3) is 30 and P3 is (7, 13, 17, 19, 23, 29) because (53, 47, 43, 41, 37, 31) are all prime. The maximum gap between two consecutive terms of P3 is 6, obtained for (7,13) or (23,29), so a(3)=6.
PROG
(PARI) lstp(n)=my(v = []); pn = prod(i=1, n, prime(i)); forprime(p=1, pn-1, if (isprime(2*pn-p), v = concat(v, p))); my(w = vector(#v-1, k, v[k+1] - v[k])); vecmax(w); \\ Michel Marcus, Jul 24 2015
(PARI) a(n)=my(P=2*prod(i=1, n, prime(i)), r, last=P); forprime(p=2, P/2, if(isprime(P-p), r=max(r, p-last); last=p)); r \\ Charles R Greathouse IV, Jul 24 2015
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Jean-Marc Rebert, Jul 24 2015
EXTENSIONS
a(10) from Charles R Greathouse IV, Jul 24 2015
a(11) from Charles R Greathouse IV, Jul 28 2015
a(12) from Charles R Greathouse IV, Jul 30 2015
STATUS
approved