A266676 Smallest span (difference between the start and end) of a symmetric n-tuple of consecutive primes.

0, 1, 4, 8, 36, 14, 60, 26, 84, 34, 132, 46, 168, 56, 180, 74, 240, 82

Offset: 1

Author

Max Alekseyev, Jan 02 2016

Keywords

• nonn
• more

Comments

An n-tuple (p(1),...,p(n)) is symmetric if p(k)+p(n+1-k) is the same for all k=1,2,...,n (cf. A175309).

In contrast to A266511, n-tuples here may be singular and give the complete set of residues modulo some prime. For example, for n=3 we have the symmetric 3-tuple: (3,5,7) = (3,3+2,3+4) of span a(3)=4, but there are no other symmetric 3-tuples of the form (p,p+2,p+4), since one of its elements would be divisible by 3.

a(n) <= A266511(n).

Crossrefs

The smallest starting primes and their indices of the corresponding tuples are given in A266583 and A266585.

Cf. A055380, A065688, A175309, A266511, A266512, A261324.