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

1,3

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).

Links

Table of n, a(n) for n=1..18.

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.

Sequence in context: A218628 A149108 A149109 * A046056 A158863 A074736

Adjacent sequences: A266673 A266674 A266675 * A266677 A266678 A266679

Keyword

nonn,more

Author

Max Alekseyev, Jan 02 2016

Status

approved