

A055380


Central prime p in the smallest (2n+1)tuple of consecutive primes that are symmetric with respect to p.


18




OFFSET

1,1


COMMENTS

Least ntuply balanced primes: primes which are averages of both their immediate neighbor, their second neighbors, their third neighbors, ... and their nth neighbors.


LINKS

Table of n, a(n) for n=1..7.


FORMULA

a(n) = A151800^(n)(A175309(2n)), i.e., A151800 applied n times on A175309(2n).  Max Alekseyev, Jul 26 2014


EXAMPLE

In 5tuple of consecutive primes (18713, 18719, 18731, 18743, 18749), the primes are symmetric w.r.t. its central prime 18731, since 18713+18749 = 18719+18743 = 2*18731, and this is the smallest such 5tuple. Hence, a(2)=18731.
Alternatively, the symmetry can be seen from the differences between consecutive primes. For (18713, 18719, 18731, 18743, 18749), the differences are (6,12,12,6).


CROSSREFS

Cf. A001223, A055381, A055382, A006562, A051795, A081415, A096710.
Sequence in context: A013834 A263684 A191940 * A201002 A246870 A193366
Adjacent sequences: A055377 A055378 A055379 * A055381 A055382 A055383


KEYWORD

more,nonn


AUTHOR

Jud McCranie, Jun 23 2000


EXTENSIONS

a(6) from Donovan Johnson, Mar 09 2008
Definition corrected by Max Alekseyev, Jul 29 2014
a(7) from Dmitry Petukhov, added by Max Alekseyev, Nov 03 2014


STATUS

approved



