login
This site is supported by donations to The OEIS Foundation.

 

Logo

Invitation: celebrating 50 years of OEIS, 250000 sequences, and Sloane's 75th, there will be a conference at DIMACS, Rutgers, Oct 9-10 2014.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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). 1
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.

Cf. A010051, A004086, A208259, A062332.

Sequence in context: A131480 A213073 A018847 * A134996 A134998 A078790

Adjacent sequences:  A178315 A178316 A178317 * A178319 A178320 A178321

KEYWORD

nonn,base,changed

AUTHOR

David Nacin, May 24 2010

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified July 24 22:06 EDT 2014. Contains 244897 sequences.