

A244442


a(n) is the smallest prime p such that all the n numbers dip(p), dip(dip(p)), ..., dip(dip(...(dip(p))...)) are primes. The function dip is defined in the comment lines.


1




OFFSET

1,1


COMMENTS

dip(m) is the number that is obtained from m by changing each zero digit of m to 1 and each nonzero digit i of m to the ith prime.
For example dip(103)=2.1.5=215 and dip(19)=2.23=223.
Since each positive integer starts with a nonzero digit, dip is well defined.


LINKS

Table of n, a(n) for n=1..6.


EXAMPLE

a(4)=834007 because the four numbers:
1. dip(834007)=19.5.7.1.1.17=19571117,
2. dip(dip(834007)),
3. dip(dip(dip(834007))),
4. dip(dip(dip(dip(834007))))
are all primes and 834007 is the smallest prime with this property.


CROSSREFS

Cf. A000040.
Sequence in context: A207820 A186069 A280842 * A246471 A079243 A289814
Adjacent sequences: A244439 A244440 A244441 * A244443 A244444 A244445


KEYWORD

nonn,base,more,hard


AUTHOR

Jahangeer Kholdi and Farideh Firoozbakht, Jul 07 2014


STATUS

approved



