A343175 a(0)=2; for n > 0, a(n) = 2^(2*n-1) + 2^n + 1.

2, 5, 13, 41, 145, 545, 2113, 8321, 33025, 131585, 525313, 2099201, 8392705, 33562625, 134234113, 536903681, 2147549185, 8590065665, 34360000513, 137439477761, 549756862465, 2199025352705, 8796097216513, 35184380477441, 140737505132545, 562949986975745, 2251799880794113

Offset: 0

Author

N. J. A. Sloane, Apr 26 2021

Keywords

• nonn
• easy

Comments

A bisection of A257418. Apart from first term, same as A085601.

Links

• Harvey P. Dale, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (7,-14,8).

Crossrefs

Cf. A257418, A085601, A343176.

Programs

Mathematica

LinearRecurrence[{7,-14,8},{2,5,13,41},30] (* Harvey P. Dale, Aug 04 2024 *)

Formula

From Chai Wah Wu, Apr 26 2021: (Start)

a(n) = 7*a(n-1) - 14*a(n-2) + 8*a(n-3) for n > 3.

G.f.: (-4*x^3 - 6*x^2 + 9*x - 2)/((x - 1)*(2*x - 1)*(4*x - 1)). (End)

Extensions

a(18)-a(26) from Martin Ehrenstein, Apr 26 2021