A220984 The right Aurifeuillian factor of 7^(14n+7) + 1.

911, 46489241, 4845303761663, 560176314330212777, 65739735996793498937711, 7731453717973685046293120441, 909551411151743369070229385367263, 107007034358477098527617255914118283977, 12589257482346423369016062830670344414194511

Offset: 0

Author

Stuart Clary, Dec 27 2012

Keywords

• nonn
• easy

Comments

The corresponding left Aurifeuillian factor is A220983.

Links

• Wikipedia, Cunningham Project
• Index entries for linear recurrences with constant coefficients, signature (137257, -2354918349, 5670354183893, -1944931485075299, 95029449572634843, -651636050170246351, 558545864083284007).

Crossrefs

Cf. A092440, A085601, A220978, A198410, A220979-A220990.

Programs

Mathematica

Table[7^(6n+3) + 7^(5n+3) + 3 * 7^(4n+2) + 7^(3n+2) + 3 * 7^(2n+1) + 7^(n+1) + 1, {n, 0, 20}]

Formula

a(n) = 7^(6n+3) + 7^(5n+3) + 3 * 7^(4n+2) + 7^(3n+2) + 3 * 7^(2n+1) + 7^(n+1) + 1.

Aurifeuillian factorization: 7^(14n+7) + 1 = (7^(2n+1) + 1) * A220983(n) * a(n).

G.f.: -(1483484787696419039*x^6 -1087259214306211086*x^5 +71725962948861585*x^4 -562870083909028*x^3 [phone]*x^2 -78551886*x +911) / ((x -1)*(7*x -1)*(49*x -1)*(343*x -1)*(2401*x -1)*(16807*x -1)*(117649*x -1)). [Colin Barker, Jan 04 2013]