A045895 Period length of pairs (a,b) where a has period 2n-2 and b has period n.

0, 2, 12, 12, 40, 30, 84, 56, 144, 90, 220, 132, 312, 182, 420, 240, 544, 306, 684, 380, 840, 462, 1012, 552, 1200, 650, 1404, 756, 1624, 870, 1860, 992, 2112, 1122, 2380, 1260, 2664, 1406, 2964, 1560

Offset: 1

Author

Ralf W. Grosse-Kunstleve

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..5000
• Ralf W. Grosse-Kunstleve, Origin of EIS sequences A045895 & A045896. [Wayback Machine copy]

Crossrefs

Cf. A045896, A204556, A204557.

Programs

Magma

[Lcm(2*n-2, n): n in [1..50]]; // G. C. Greubel, Jun 15 2018

Mathematica

Table[ LCM[ 2*n-2, n ], {n, 40} ]

PARI

for(n=1, 50, print1(lcm(2*n-2, n), ", ")) \\ G. C. Greubel, Jun 15 2018

Formula

a(n) = A204557(n) - A204556(n). - Reinhard Zumkeller, Jan 18 2012

From Amiram Eldar, Sep 14 2022: (Start)

a(n) = n*(n-1) for n even.

a(n) = 2*n*(n-1) for n odd.

a(n) = lcm(2*n-2, n).

a(n) = 2*A045896(n-2).

Sum_{n>=2} 1/a(n) = (log(2)+1)/2. (End)