A089985 a(n) = A089709(n+1)/A089709(n).

2, 3, 6, 10, 18, 34, 66, 130, 258, 514, 1026, 2050, 4098, 8194, 16386, 32770, 65538, 131074, 262146, 524290, 1048578, 2097154, 4194306, 8388610, 16777218, 33554434, 67108866, 134217730, 268435458, 536870914, 1073741826, 2147483650, 4294967298, 8589934594

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..2000

Index entries for linear recurrences with constant coefficients, signature (3,-2).

Formula

a(n) = 2^(n-1) + 2, n>2.

From Elmo R. Oliveira, Jun 17 2026: (Start)

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

E.g.f.: (exp(2*x) + 4*exp(x) - 5 - 2*x - x^2)/2.

a(n) = 3*a(n-1) - 2*a(n-2) for n > 4. (End)

Mathematica

Join[{2, 3}, Rest[2^Range[40]+2]] (* Harvey P. Dale, Sep 19 2011 *)

Crossrefs

Cf. A089709.

Essentially the same as A056469.

Sequence in context: A054152 A240802 A339808 * A191518 A217382 A378672

Adjacent sequences: A089982 A089983 A089984 * A089986 A089987 A089988

Keyword

nonn,easy,changed

Author

Ray Chandler, Nov 21 2003

Status

approved