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A098937
Number of cyclic numbers, primes with primitive root 10, (A001913) in the first 10^n primes (A000040).
0
5, 38, 387, 3755, 37523, 374126, 3740610, 37393725, 373953691, 3739544360
OFFSET
1,1
FORMULA
Lim_{n->oo} a(n)/10^n = Artin's constant (A005596).
MATHEMATICA
f[n_Integer] := Block[{ds = Divisors[n - 1]}, (n - 1)/Take[ds, Position[ PowerMod[10, ds, n], 1][[1, 1]]][[ -1]]]; c = 0; k = 4; Do[ While[k <= 10^n, a = f[ Prime[k]]; If[a == 1, c++ ]; k++ ]; Print[c], {n, 7}]
CROSSREFS
KEYWORD
base,more,nonn
AUTHOR
Robert G. Wilson v, Oct 19 2004
EXTENSIONS
a(8)-a(10) from Amiram Eldar, Jul 04 2021
STATUS
approved