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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A134136 a(n) = 2*a(n-2) + 4*a(n-3), with initial terms 0, 1, 1. 2
 0, 1, 1, 2, 6, 8, 20, 40, 72, 160, 304, 608, 1248, 2432, 4928, 9856, 19584, 39424, 78592, 157184, 314880, 628736, 1258496, 2516992, 5031936, 10067968, 20131840, 40263680, 80535552, 161054720, 322125824, 644251648, 1288470528, 2577006592, 5153947648, 10307895296 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS Robert Israel, Table of n, a(n) for n = 0..2991 Index entries for linear recurrences with constant coefficients, signature (0,2,4). FORMULA a(n) = (6*2^n - (3+i)*(-1+i)^n - (3-i)*(-1-i)^n)/20. - Ivan Neretin, May 27 2015 G.f.: (x^2+x)/(1-2*x^2-4*x^3). - Robert Israel, May 27 2015 MAPLE f:= gfun:-rectoproc({a(n)=2*a(n-2)+4*a(n-3), a(0)=0, a(1)=1, a(2)=1}, a(n), remember): seq(f(n), n=0..100); # Robert Israel, May 27 2015 MATHEMATICA Nest[Append[#, 2 #[[-2]] + 4 #[[-3]]] &, {0, 1, 1}, 15] (* Ivan Neretin, May 27 2015 *) CoefficientList[Series[x (1 + x)/((1 - 2 x) (2 x^2 + 2 x + 1)), {x, 0, 40}], x] (* Vincenzo Librandi, May 28 2015 *) PROG (MAGMA) [n le 3 select Floor(n/2) else 2*Self(n-2)+4*Self(n-3): n in [1..40]]; // Vincenzo Librandi, May 28 2015 CROSSREFS Cf. A134654. Sequence in context: A064713 A162213 A100358 * A185165 A289892 A289095 Adjacent sequences:  A134133 A134134 A134135 * A134137 A134138 A134139 KEYWORD nonn,easy AUTHOR Paul Curtz, Jan 29 2008 EXTENSIONS More terms from Robert Israel, May 27 2015 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 August 8 11:31 EDT 2020. Contains 336298 sequences. (Running on oeis4.)