A178318 Primes which remain prime after reflection across a vertical line through the middle of the number (numbers are written as digital clock style numerals).

2, 5, 11, 101, 181, 1051, 1181, 1201, 1811, 10151, 11251, 11551, 12101, 12211, 12511, 15121, 18181, 100151, 100501, 101501, 101581, 102001, 102101, 102181, 102551, 105211, 105251, 108881, 110051, 110581, 110881, 111521, 111581, 115021, 115201

Offset

1,1

Comments

Apart from first two terms: subsequence of A208259. - Reinhard Zumkeller, Jul 16 2014

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

Example

For example 1051 becomes 1201 under this reflection and since these are both prime, these number are part of the sequence. Note that a number must be composed only of the digits 0,1,2,5,8 to qualify.

Prog

(Haskell)
import Data.List (intersect, genericIndex)
a178318 n = a178318_list !! (n-1)
a178318_list = 2 : 5 : filter f a062332_list where
   f p = null (show p `intersect` "34679") && a010051' (r 0 p) == 1
   r y 0 = y
   r y x = r (10 * y + genericIndex [0, 1, 5, 0, 0, 2, 0, 0, 8, 0] d) x'
             where (x', d) = divMod x 10
-- Reinhard Zumkeller, Jul 16 2014

Crossrefs

Cf. A125308, A178317.

Cf. A010051, A004086, A208259, A062332.

Sequence in context: A286453 A309375 A018847 * A134996 A134998 A078790

Adjacent sequences: A178315 A178316 A178317 * A178319 A178320 A178321

Keyword

nonn,base

Author

David Nacin, May 24 2010

Status

approved