The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A055382 Smallest prime starting a sequence of 2n consecutive odd primes with symmetrical gaps about the center. 14
 3, 5, 5, 17, 13, 137, 8021749, 1071065111, 1613902553, 1797595814863, 633925574060671, 22930603692243271 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(13) <= 5179852391836338871. The solution was found by the BOINC project "SPT test project". - Natalia Makarova, Dec 06 2023 LINKS Table of n, a(n) for n=1..12. Discussion at the scientific forum dxdy.ru, Distributed computing project (in Russian) Symmetric Prime Tuples, SPT test project Index entries for primes, gaps between FORMULA For n>1, a(n) = A081235(n) = A175309(2n-1). 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 Cf. A001223, A055380, A055381, A175309. See A081235 for another version. Sequence in context: A318351 A137780 A079372 * A165235 A370553 A200771 Adjacent sequences: A055379 A055380 A055381 * A055383 A055384 A055385 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified July 23 12:38 EDT 2024. Contains 374549 sequences. (Running on oeis4.)