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

1,1

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)

Prog

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

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.

Sequence in context: A337189 A087358 A391596 * A255357 A270002 A057736

Adjacent sequences: A379641 A379642 A379643 * A379645 A379646 A379647

Keyword

nonn

Author

Sean A. Irvine, Dec 28 2024

Status

approved