A379642 Smallest primitive prime factor of 9^n-1.

2, 5, 7, 41, 11, 73, 547, 17, 19, 1181, 23, 6481, 398581, 29, 31, 21523361, 103, 530713, 1597, 42521761, 43, 5501, 47, 97, 151, 53, 109, 430697, 59, 47763361, 683, 926510094425921, 25411, 956353, 71, 282429005041, 18427, 5301533, 79, 14401, 83, 2857, 431, 89

Offset: 1

Author

Sean A. Irvine, Dec 28 2024

Keywords

• nonn

Comments

Also, smallest prime p such that 1/p has nonary period n.

Links

• Max Alekseyev, Table of n, a(n) for n = 1..730 (first 690 terms from Sean A. Irvine)

Crossrefs

Cf. A112927 (base 2), A143663 (base 3), A112092 (base 4), A143665 (base 5), A379639 (base 6), A379640 (base 7), A379641 (base 8), A379642 (base 9), A007138 (base 10), A379644 (base 11), A252170 (base 12).

Cf. A274909.

Programs

PARI

listap(nn) = {prf = []; for (n=1, nn, vp = (factor(9^n-1)[, 1])~; f = setminus(Set(vp), Set(prf)); prf = concat(prf, f); print1(vecmin(Vec(f)), ", "); ); }