OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..300
Index entries for linear recurrences with constant coefficients, signature (0, 6).
FORMULA
a(n) = 6^(1/4*(2*n+3+(-1)^n))*(25-23*(-1)^n)/72.
G.f.: x*(4+x)/(1-6*x^2).
MATHEMATICA
Join[{4, 1, 24}, LinearRecurrence[{0, 6}, {6, 144}, 25]] (* G. C. Greubel, Apr 21 2016 *)
PROG
(Magma) [ n le 2 select 7-3*n else 6*Self(n-2): n in [1..29] ];
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Klaus Brockhaus, Oct 04 2009
STATUS
approved