OFFSET
1,1
COMMENTS
Phi(10,k) = k^4 - k^3 + k^2 - k + 1.
Note that except for a(3), all terms end with the digit 1.
LINKS
Robert Price, Table of n, a(n) for n = 1..1218
MATHEMATICA
prim = {}; Do[prim = Join[prim, Complement[First /@ FactorInteger[Cyclotomic[10, k]], prim]], {k, 1000}]; prim
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert Price, Mar 14 2015
STATUS
approved