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A163888
a(n) = 2*a(n-2) for n > 2; a(1) = 5, a(2) = 4.
6
5, 4, 10, 8, 20, 16, 40, 32, 80, 64, 160, 128, 320, 256, 640, 512, 1280, 1024, 2560, 2048, 5120, 4096, 10240, 8192, 20480, 16384, 40960, 32768, 81920, 65536, 163840, 131072, 327680, 262144, 655360, 524288, 1310720, 1048576, 2621440, 2097152, 5242880
OFFSET
1,1
COMMENTS
Interleaving of A020714 and A000079 without initial terms 1 and 2.
Binomial transform is A163607, second binomial transform is A163608, third binomial transform is A163609, fourth binomial transform is A163610, fifth binomial transform is A163611.
FORMULA
a(n) = (7 - 3*(-1)^n)*2^((2*n-5+(-1)^n)/4).
G.f.: x*(5+4*x)/(1-2*x^2).
MATHEMATICA
Transpose[NestList[{Last[#], 2First[#]}&, {5, 4}, 40]] [[1]] (* Harvey P. Dale, Mar 14 2011 *)
LinearRecurrence[{0, 2}, {5, 4}, 41] (* Ray Chandler, Aug 14 2015 *)
PROG
(Magma) [ n le 2 select 6-n else 2*Self(n-2): n in [1..41] ];
(PARI) x='x+O('x^50); vec(x*(5+4*x)/(1-2*x^2)) \\ G. C. Greubel, Aug 07 2017
CROSSREFS
Cf. A020714 (5*2^n), A000079 (powers of 2), A163607, A163608, A163609, A163610, A163611.
Sequence in context: A286461 A152064 A088482 * A363323 A309545 A285105
KEYWORD
nonn
AUTHOR
Klaus Brockhaus, Aug 06 2009
STATUS
approved