A332491 a(n) = 2*a(n-1) + a(n-3), where a(0) = 3, a(1) = 1, a(2) = 2.

3, 1, 2, 7, 15, 32, 71, 157, 346, 763, 1683, 3712, 8187, 18057, 39826, 87839, 193735, 427296, 942431, 2078597, 4584490, 10111411, 22301419, 49187328, 108486067, 239273553, 527734434, 1163954935, 2567183423, 5662101280, 12488157495, 27543498413

Offset: 0

Author

Michael Tulskikh, Feb 13 2020

Keywords

• nonn
• easy

Links

• Index entries for linear recurrences with constant coefficients, signature (2,0,1).

Programs

Mathematica

LinearRecurrence[{2,0,1},{3,1,2},40] (* Harvey P. Dale, Apr 20 2025 *)

Formula

a(n) = 2*a(n-1) + a(n-3).

a(n) = A052980(n) + 2*A008998(n-3).

a(n) = A008998(n-1) + 3*A008998(n-3).

G.f.: (5x-3)/(x^3+2*x-1).