This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A103321 Expansion of 1 / ((1-x-x^2-x^3)*(1-x-x^3)). 1
 1, 2, 4, 9, 18, 35, 68, 130, 246, 463, 867, 1617, 3007, 5579, 10332, 19107, 35295, 65140, 120137, 221444, 407999, 751453, 1383641, 2547116, 4688106, 8627504, 15875390, 29209560, 53739655, 98864470, 181872110, 334561861, 615423932 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 REFERENCES A. T. Benjamin and J. J. Quinn, Proofs that really count: the art of combinatorial proof, M.A.A. 2003, p. 47, ex. 4. LINKS G. C. Greubel, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (2, 0, 1, -2, -1, -1). FORMULA a(n) = A000073(n+4) - A000930(n+2). a(n) = Sum_{k=0..n} A000073(k+2)*A000930(n-k). a(0)=1, a(1)=2, a(2)=4, a(3)=9, a(4)=18, a(5)=35, a(n)=2*a(n-1)+a(n-3)- 2*a(n-4)-a(n-5)-a(n-6). - Harvey P. Dale, Nov 06 2011 MATHEMATICA CoefficientList[Series[1/((1-x-x^2-x^3)(1-x-x^3)), {x, 0, 40}], x] (* or *) LinearRecurrence[{2, 0, 1, -2, -1, -1}, {1, 2, 4, 9, 18, 35}, 40] (* Harvey P. Dale, Nov 06 2011 *) PROG (PARI) x='x+O('x^50); Vec(1/((1-x-x^2-x^3)*(1-x-x^3))) \\ G. C. Greubel, May 02 2017 CROSSREFS Sequence in context: A046683 A065055 A065030 * A138196 A298404 A101351 Adjacent sequences:  A103318 A103319 A103320 * A103322 A103323 A103324 KEYWORD nonn AUTHOR Ralf Stephan, Feb 02 2005 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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified October 23 04:27 EDT 2018. Contains 316519 sequences. (Running on oeis4.)