This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A087170 Expansion of (1 + 4*x)/(1 + 7*x + 16*x^2). 0
 1, -3, 5, 13, -171, 989, -4187, 13485, -27403, -23939, 606021, -3859123, 17317525, -59476707, 139256549, -23168531, -2065925067, 14832171965, -70770402683, 258078067341, -674220028459, 590291121757, 6655482603045, -56033036169427, 285743531537269, -1103676142050051 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS For positive n, a(n) equals 4^n times the permanent of the (2n) X (2n) matrix with 1/2's along the main diagonal, and i's along the superdiagonal and the subdiagonal (where i is the imaginary unit). - John M. Campbell, Jul 08 2011 LINKS Index entries for linear recurrences with constant coefficients, signature (-7,-16). FORMULA G.f.: (1 + 4*x)/(1 + 7*x + 16*x^2). a(n) = -7*a(n-1) - 16*a(n-2), a(0)=1, a(1)=-3. a(n) = Sum_{k=0..n} binomial(n+k,2*k)*(-4)^(n-k). a(n) = -((1/30)*i)*sqrt(15)*(-7/2+(1/2)*i*sqrt(15))^n+(1/2)*(-7/2+(1/2)*i*sqrt(15))^n+(1/2)*(-7/2-(1/2)*i*sqrt(15))^n+((1/30)*i)*sqrt(15)*(-7/2-(1/2)*i*sqrt(15))^n, with n>=0 and i=sqrt(-1). - Paolo P. Lava, Jun 12 2008 MATHEMATICA CoefficientList[Series[(1 + 4x)/(16x^2 + 7x + 1), {x, 0, 25}], x] CROSSREFS Sequence in context: A155012 A121533 A187733 * A123370 A110407 A062698 Adjacent sequences:  A087167 A087168 A087169 * A087171 A087172 A087173 KEYWORD easy,sign AUTHOR Mario Catalani (mario.catalani(AT)unito.it), Aug 22 2003 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.

Last modified June 19 11:11 EDT 2019. Contains 324219 sequences. (Running on oeis4.)