

A166850


Numbers n such that reversal(n!n) is prime.


0




OFFSET

1,1


COMMENTS

It's obvious that there is no number n such that n!n is prime.
There is no further term up to 5000.


LINKS

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


EXAMPLE

56!56=
710998587804863451854045647463724949736497978881168458687447039999999999944
and reversal(56!56)=
449999999999930744786854861188879794637949427364746540458154368408785899017
is prime so 56 is in the sequence.


MATHEMATICA

reversal[n_]:=FromDigits[Reverse[IntegerDigits[n]]];
Do[If[PrimeQ[reversal[n!n]], Print[n]], {n, 5000}]


CROSSREFS

Sequence in context: A114694 A272337 A132678 * A317856 A331725 A067093
Adjacent sequences: A166847 A166848 A166849 * A166851 A166852 A166853


KEYWORD

base,hard,more,nonn


AUTHOR

Farideh Firoozbakht, Oct 22 2009


STATUS

approved



