A379641 Smallest primitive prime factor of 8^n-1.

7, 3, 73, 5, 31, 19, 127, 17, 262657, 11, 23, 37, 79, 43, 631, 97, 103, 87211, 32377, 41, 92737, 67, 47, 433, 601, 2731, 2593, 29, 233, 18837001, 2147483647, 193, 199, 307, 71, 246241, 223, 571, 937, 61681, 13367, 77158673929, 431, 397, 271, 139, 2351, 577

Offset

1,1

Comments

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

Links

Max Alekseyev, Table of n, a(n) for n = 1..548 (first 500 terms from Sean A. Irvine)

Prog

(PARI) listap(nn) = {prf = []; for (n=1, nn, vp = (factor(8^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. A274908.

Sequence in context: A248279 A372617 A381493 * A183421 A173443 A003723

Adjacent sequences: A379638 A379639 A379640 * A379642 A379643 A379644

Keyword

nonn

Author

Sean A. Irvine, Dec 28 2024

Status

approved