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A055382 Smallest prime starting a sequence of 2n consecutive odd primes with symmetrical gaps about the center. 7
3, 5, 5, 17, 13, 137, 8021749, 1071065111, 1613902553, 1797595814863, 633925574060671, 22930603692243271 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..12.

Discussion at the scientific forum dxdy.ru, Distributed computing project (in Russian)

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.

CROSSREFS

Cf. A001223, A055380, A055381, A175309.

See A081235 for another version.

Sequence in context: A028254 A137780 A079372 * A165235 A200771 A072624

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

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Last modified March 22 22:17 EDT 2017. Contains 283901 sequences.