A162396 a(n) = 2*a(n-2) for n > 2; a(1) = 5, a(2) = 2.
5, 2, 10, 4, 20, 8, 40, 16, 80, 32, 160, 64, 320, 128, 640, 256, 1280, 512, 2560, 1024, 5120, 2048, 10240, 4096, 20480, 8192, 40960, 16384, 81920, 32768, 163840, 65536, 327680, 131072, 655360, 262144, 1310720, 524288, 2621440, 1048576, 5242880
Offset: 1
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..1000
- Index entries for linear recurrences with constant coefficients, signature (0,2).
Programs
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Magma
[ n le 2 select 8-3*n else 2*Self(n-2): n in [1..41] ];
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Magma
[Floor((3/2-(-1)^n)*2^(1/4*(2*n+3+(-1)^n))): n in [1..50]]; // Vincenzo Librandi, Oct 09 2017
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Maple
A162396:=n->(3/2-(-1)^n)*2^(1/4*(2*n+3+(-1)^n)): seq(A162396(n), n=1..60); # Wesley Ivan Hurt, Oct 08 2017
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Mathematica
CoefficientList[Series[(5 + 2*x)/(1 - 2*x^2), {x, 0, 40}], x] (* Wesley Ivan Hurt, Oct 08 2017 *) RecurrenceTable[{a[1]==5, a[2]==2, a[n]==2 a[n-2]}, a, {n, 40}] (* Vincenzo Librandi, Oct 09 2017 *)
Formula
a(n) = (3/2-(-1)^n)*2^(1/4*(2*n+3+(-1)^n)).
G.f.: x*(5+2*x)/(1-2*x^2).
Extensions
G.f. corrected, formula simplified, comment added by Klaus Brockhaus, Sep 18 2009
Comments