OFFSET
1,1
COMMENTS
From Robert Israel, Jul 25 2019: (Start)
If n is in the sequence and is not divisible by 10, then A004086(n) is in the sequence.
All terms except 2 are divisible by 3. (End)
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
12 is a term because 12*21-1=251 is prime.
MAPLE
revdigs:= proc(n) local L, i;
L:= convert(n, base, 10);
add(L[-i]*10^(i-1), i=1..nops(L))
end proc:
select(t -> isprime(t*revdigs(t)-1), [$1..1000]); # Robert Israel, Jul 25 2019
MATHEMATICA
Select[Range[800], PrimeQ[# IntegerReverse[#]-1]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jul 05 2020 *)
CROSSREFS
KEYWORD
easy,base,nonn
AUTHOR
Shyam Sunder Gupta, Aug 23 2002
STATUS
approved