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

1,1

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)

Prog

(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)), ", "); ); }

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.

Sequence in context: A123232 A042559 A197222 * A062645 A174259 A215213

Adjacent sequences: A379639 A379640 A379641 * A379643 A379644 A379645

Keyword

nonn

Author

Sean A. Irvine, Dec 28 2024

Status

approved