OFFSET
1,1
COMMENTS
a(n) < prime(n) for n > 1. This is true since prime(n) in base prime(n)-1 is written as 11 which is an absolute prime.
Conjecture: a(n) < prime(n)-1 for n > 2.
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..10000
Wikipedia, Permutable prime
EXAMPLE
a(78) = 13. prime(78) = 397 in base 10 and 397_10 = 247_13. Rearranging the digits in base 13, we get 274_13 = 433_10, 427_13 = 709_10, 472_13 = 769_10, 724_13 = 1213_10, 742_13 = 1237_10, all of which are prime.
CROSSREFS
KEYWORD
nonn
AUTHOR
Chai Wah Wu, Jun 11 2015
STATUS
approved