A246398 - OEIS

A246398

Smallest number of digits that have to be inserted into or prepended to decimal representation of n, to get a prime.

2, 1, 0, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 2, 1, 0, 0, 1, 1, 1, 1, 1, 0, 1, 0, 2, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 2, 1, 1, 1, 0, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 2, 1

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OFFSET

0,1

COMMENTS

a(n) = 0 iff n is a prime number, a(A000040(n)) = 0;

a(n) = A055642(A062584(n)) - A055642(n).

LINKS

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

PROG

(Haskell)

a246398 n = a246398_list !! n

a246398_list = f 0 $ map show a000040_list where