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A162766
a(n) = 3*a(n-2) for n > 2; a(1) = 4, a(2) = 3.
9
4, 3, 12, 9, 36, 27, 108, 81, 324, 243, 972, 729, 2916, 2187, 8748, 6561, 26244, 19683, 78732, 59049, 236196, 177147, 708588, 531441, 2125764, 1594323, 6377292, 4782969, 19131876, 14348907, 57395628, 43046721, 172186884, 129140163
OFFSET
1,1
COMMENTS
Binomial transform is A162559. Second binomial transform is A077236.
FORMULA
a(n) = (5-3*(-1)^n)*3^(1/4*(2*n-1+(-1)^n))/2.
G.f.: x*(4+3*x)/(1-3*x^2).
a(n) = A074324(n+1) = A166552(n+1) = 3^floor(n/2)*4^(n%2), where n%2 = 0 for n even, 1 for n odd. - M. F. Hasler, Dec 03 2014
PROG
(Magma) [ n le 2 select 5-n else 3*Self(n-2): n in [1..34] ];
(PARI) a(n)=3^(n\2)*4^(n%2) \\ M. F. Hasler, Dec 03 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Klaus Brockhaus, Jul 13 2009
EXTENSIONS
G.f. corrected by Klaus Brockhaus, Sep 18 2009
STATUS
approved