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A098575 a(n) = Sum_{k=0..floor(n/4)} C(n-2*k,2*k)*2^k. 4
1, 1, 1, 1, 3, 7, 13, 21, 35, 63, 117, 213, 379, 671, 1197, 2149, 3859, 6911, 12357, 22101, 39563, 70847, 126845, 227045, 406371, 727391, 1302101, 2330901, 4172443, 7468767, 13369293, 23931621, 42838835, 76683583, 137266917, 245713493 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,5
LINKS
FORMULA
G.f.: (1-x)/((1-x)^2-2*x^4).
a(n) = 2*a(n-1) - a(n-2) + 2*a(n-4).
MATHEMATICA
CoefficientList[Series[(1-x)/((1-x)^2-2x^4), {x, 0, 40}], x] (* Vincenzo Librandi, Jun 17 2012 *)
PROG
(Magma) I:=[1, 1, 1, 1]; [n le 4 select I[n] else 2*Self(n-1)-Self(n-2)+2*Self(n-4): n in [1..40]]; // Vincenzo Librandi, Jun 17 2012
(PARI) x='x+O('x^30); Vec((1-x)/((1-x)^2-2*x^4)) \\ G. C. Greubel, Feb 03 2018
CROSSREFS
Sequence in context: A060939 A174030 A355734 * A363144 A138035 A355736
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Sep 16 2004
STATUS
approved

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Last modified March 29 09:14 EDT 2024. Contains 371268 sequences. (Running on oeis4.)