OFFSET
1,1
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..130 (terms < 10^15)
MATHEMATICA
Select[Range[400000], PowerMod[10, EulerPhi[#], #^2] == 1 &] (* Amiram Eldar, Oct 16 2023 *)
PROG
(PARI) for(n=2, 1e9, if(Mod(10, n^2)^(eulerphi(n))==1, print1(n, ", ")))
CROSSREFS
KEYWORD
nonn
AUTHOR
Felix Fröhlich, Aug 10 2014
EXTENSIONS
Terms a(12) and beyond from Giovanni Resta, Jan 24 2020
STATUS
approved