A066845 a(n) = (lcm_{k=0..n} (2^k + 1))/(lcm_{k=0..n-1} (2^k + 1)).

3, 5, 3, 17, 11, 13, 43, 257, 57, 205, 683, 241, 2731, 3277, 331, 65537, 43691, 4033, 174763, 61681, 5419, 838861, 2796203, 65281, 1016801, 13421773, 261633, 15790321, 178956971, 80581, 715827883, 4294967297, 1397419, 3435973837

Offset

1,1

Comments

The primitive part of 2^n + 1. Bisection of A019320. - T. D. Noe, Jul 24 2008

Links

T. D. Noe, Table of n, a(n) for n = 1..1000

Formula

a(n) = cyclotomic(2*n, 2). - Vladeta Jovovic, Apr 05 2004

Mathematica

Cyclotomic[2*Range[40], 2] (* Harvey P. Dale, Apr 19 2019 *)

Prog

(PARI) a(n) = polcyclo(2*n, 2); \\ Michel Marcus, Mar 06 2015

Crossrefs

Cf. A051844, A034268, A019320.

Cf. A019320.

Sequence in context: A244801 A002586 A258811 * A014782 A348591 A094466

Adjacent sequences: A066842 A066843 A066844 * A066846 A066847 A066848

Keyword

easy,nonn

Author

Vladeta Jovovic, Jan 20 2002

Status

approved