%I #27 Jul 30 2015 10:26:15

%S 6,16,44,122,268,556,886,1446,1964,2900

%N Maximal gap between successive elements of Pn with n >= 3. Pn : primes p <= A002110(n) such that q=2*A002110(n)-p is prime. (p, q) is a pair of centered primes at n-th primorial.

%e 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.

%o (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

%o (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

%Y Cf. A002110.

%K nonn,more

%O 3,1

%A _Jean-Marc Rebert_, Jul 24 2015

%E a(10) from _Charles R Greathouse IV_, Jul 24 2015

%E a(11) from _Charles R Greathouse IV_, Jul 28 2015

%E a(12) from _Charles R Greathouse IV_, Jul 30 2015