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!)
A026385 Sum{T(n-k,k)}, 0<=k<=[ n/2 ], where T is the array in A026374. 3
1, 1, 2, 4, 6, 11, 20, 33, 59, 104, 178, 314, 549, 952, 1669, 2913, 5074, 8872, 15482, 27007, 47172, 82325, 143675, 250848, 437822, 764198, 1334041, 2328512, 4064457, 7094833, 12384034, 21616716, 37732990, 65863651 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (0,1,3,1).

FORMULA

G.f.: (1+x+x^2)/(1-x^2-3x^3-x^4). - Ralf Stephan, Apr 30 2004

a(n) = a(n-2) + 3*a(n-3) + a(n-4) for n>3. - Vincenzo Librandi, Jun 19 2014

MATHEMATICA

LinearRecurrence[{0, 1, 3, 1}, {1, 1, 2, 4}, 40] (* Harvey P. Dale, Jun 18 2014 *)

CoefficientList[Series[(1 + x + x^2)/(1 - x^2 - 3 x^3 - x^4), {x, 0, 40}], x] (* Vincenzo Librandi, Jun 19 2014 *)

PROG

(MAGMA) I:=[1, 1, 2, 4]; [n le 4 select I[n] else Self(n-2)+3*Self(n-3)+Self(n-4): n in [1..40]]; // Vincenzo Librandi, Jun 19 2014

CROSSREFS

Sequence in context: A113913 A002097 A026757 * A254532 A199926 A068330

Adjacent sequences:  A026382 A026383 A026384 * A026386 A026387 A026388

KEYWORD

nonn

AUTHOR

Clark Kimberling

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 February 24 04:36 EST 2020. Contains 332197 sequences. (Running on oeis4.)