OFFSET
1,1
COMMENTS
Also, smallest prime p such that 1/p has duodecimal period n.
LINKS
Max Alekseyev, Table of n, a(n) for n = 1..310
EXAMPLE
a(4) = 5 because 1/5 = 0.249724972497... and 5 is the smallest prime with period 4 in base 12.
a(5) = 22621 because 1/22621 = 0.0000100001... and 22621 is the smallest (in fact, the only one) prime with period 5 in base 12.
MAPLE
S:= {}:
for n from 1 to 72 do
F:= numtheory:-factorset(12^n-1) minus S;
A[n]:= min(F);
S:= S union F;
od:
seq(A[n], n=1..72);
MATHEMATICA
prms={}; Table[f=First/@FactorInteger[12^n-1]; p=Complement[f, prms]; prms=Join[prms, p]; If[p=={}, 1, First[p]], {n, 72}]
PROG
(PARI) listap(nn) = {prf = []; for (n=1, nn, vp = (factor(12^n-1)[, 1])~; f = setminus(Set(vp), Set(prf)); prf = concat(prf, f); print1(vecmin(Vec(f)), ", "); ); } \\ Michel Marcus, Dec 15 2014; after A007138
CROSSREFS
KEYWORD
nonn
AUTHOR
Eric Chen, Dec 15 2014
EXTENSIONS
Edited by Max Alekseyev, Aug 26 2021
STATUS
approved