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A097068
a(n)=Sum(C(n,2k+1)5^k 3^(2k+1) 7^(n-2k-1), k=0,..,Floor[(n-1)/2]).
0
0, 3, 42, 576, 7896, 108240, 1483776, 20339904, 278823552, 3822170112, 52395087360, 718242542592, 9845815246848, 134968443285504, 1850174945009664, 25362575456993280, 347675356617867264
OFFSET
0,2
FORMULA
a(n)=2^(n-1)F(4n), where F(n) are Fibonacci numbers A000045
a(n)= 14*a(n-1) -4*a(n-2). G.f.: 3*x/(1-14*x+4*x^2). [From R. J. Mathar, Feb 06 2010]
MATHEMATICA
Table[Sum[Binomial[n, 2k + 1]5^k 3^(2k + 1)7^(n-2k-1), {k, 0, Floor[(n - 1)/2]}], {n, 0, 25}]
CROSSREFS
Sequence in context: A003770 A173936 A219619 * A269046 A092470 A355796
KEYWORD
easy,nonn
AUTHOR
Mario Catalani (mario.catalani(AT)unito.it), Jul 22 2004
STATUS
approved