A379644 Smallest primitive prime factor of 11^n-1.

2, 3, 7, 61, 3221, 37, 43, 7321, 1772893, 13421, 15797, 13, 1093, 1623931, 195019441, 17, 50544702849929377, 590077, 6115909044841454629, 212601841, 1723, 23, 829, 10657, 3001, 53, 5559917315850179173, 29, 523, 31, 50159, 51329, 661, 71707, 211, 3138426605161

Offset: 1

Author

Sean A. Irvine, Dec 28 2024

Keywords

• nonn

Comments

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

Links

• Max Alekseyev, Table of n, a(n) for n = 1..330 (first 253 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. A274910.

Programs

PARI

listap(nn) = {prf = []; for (n=1, nn, vp = (factor(11^n-1)[, 1])~; f = setminus(Set(vp), Set(prf)); prf = concat(prf, f); print1(vecmin(Vec(f)), ", "); ); }