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
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
Programs
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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
Comments