OFFSET
1,1
COMMENTS
a(13) <= 5179852391836338871. The solution was found by the BOINC project "SPT test project". - Natalia Makarova, Dec 06 2023
LINKS
Discussion at the scientific forum dxdy.ru, Distributed computing project (in Russian)
Symmetric Prime Tuples, SPT test project
EXAMPLE
The first term is 3 since the 2 primes 3, 5 have a gap of 2, which is trivially symmetric about its center.
The second term is 5 since the 4 primes 5, 7, 11, 13 have gaps 2, 4, 2, which is symmetric about its center.
The twelve primes 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193 have gaps 2, 10, 2, 6, 6, 4, 6, 6, 2, 10, 2 - symmetric about the middle, so a(6) = 137.
MATHEMATICA
Table[i = 1;
While[x = Differences[Table[Prime[k + i], {k, 2 n}]];
x != Reverse[x], i++]; Prime[i + 1], {n, 6}] (* Robert Price, Oct 12 2019 *)
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Jud McCranie, Jun 23 2000
EXTENSIONS
a(10) from Donovan Johnson, Mar 09 2008
Minor edits by N. J. A. Sloane, Apr 02 2010
a(11) from Dmitry Petukhov, added by Max Alekseyev, Aug 08 2014
a(12) from an anonymous participant of the project, added by Max Alekseyev, Jul 21 2015
STATUS
approved