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

Author

David Nacin, May 24 2010

Keywords

• nonn
• base

Comments

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

Examples

			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.
		

Links

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

Crossrefs

Cf. A125308, A178317.

Cf. A010051, A004086, A208259, A062332.

Programs

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