A178318 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

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.