A211396 Smallest prime substring of n, or 0 if no such substring exists.

0, 0, 2, 3, 0, 5, 0, 7, 0, 0, 0, 11, 2, 3, 0, 5, 0, 7, 0, 19, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 2, 3, 3, 3, 3, 3, 3, 3, 0, 41, 2, 3, 0, 5, 0, 7, 0, 0, 5, 5, 2, 3, 5, 5, 5, 5, 5, 5, 0, 61, 2, 3, 0, 5, 0, 7, 0, 0, 7, 7, 2, 3, 7, 5, 7, 7, 7, 7, 0, 0, 2, 3, 0, 5

Offset: 0

Author

Reinhard Zumkeller, Feb 08 2013

Keywords

• nonn
• base
• look

Comments

a(n) <= A047814(n);

a(n) = 0 iff A039997(n) = 0, cf. A062115;

a(n) = n iff n is prime and A039997(n) = 1.

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Programs

Haskell

import Data.List (isInfixOf)
a211396 n = if null ips then 0 else head ips
   where ips = [p | p <- takeWhile (<= n) a000040_list,
                    show p `isInfixOf` show n]