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A260384
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.
1
6, 16, 44, 122, 268, 556, 886, 1446, 1964, 2900
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
Cf. A002110.
Sequence in context: A317758 A010915 A352115 * A126360 A264545 A296855
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