login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A019481 a(n) = 3*a(n-1) + a(n-2) - 2*a(n-3) (agrees with A019480 for n <= 19 only). 4
4, 12, 37, 115, 358, 1115, 3473, 10818, 33697, 104963, 326950, 1018419, 3172281, 9881362, 30779529, 95875387, 298642966, 930245227, 2897627873, 9025842914, 28114666161, 87574585651, 272786737286, 849705465187, 2646753961545, 8244393875250 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

REFERENCES

R. K. Guy, personal communication.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (3,1,-2)

FORMULA

From R. J. Mathar, Aug 22 2008: (Start)

O.g.f.: (4 - 3*x^2)/(1 - 3*x - x^2 + 2*x^3).

a(n) = 4*A100058(n) - 3*A100058(n-2). (End)

MATHEMATICA

LinearRecurrence[{3, 1, -2}, {4, 12, 37}, 30] (* Harvey P. Dale, Jan 17 2017 *)

PROG

(MAGMA) I:=[4, 12, 37]; [n le 3 select I[n] else 3*Self(n-1)+Self(n-2)-2*Self(n-3): n in [1..30]]; // Vincenzo Librandi, Jan 18 2017

CROSSREFS

Sequence in context: A033130 A196918 A099098 * A019480 A192907 A280891

Adjacent sequences:  A019478 A019479 A019480 * A019482 A019483 A019484

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 29 21:32 EDT 2020. Contains 333117 sequences. (Running on oeis4.)