OFFSET
1,2
COMMENTS
Binomial transform = A134418: (1, 5, 14, 48, 152, 496, 1600, ...). Double binomial transform = A048875: (1, 6, 25, 106, 449, 1902, ...) - Gary W. Adamson, Oct 24 2007
LINKS
FORMULA
The following formulas are given for a general natural parameter p > 1 (p = 5 for this sequence).
G.f.: g(x) = x(1+(p-1)x)/(1-px^2).
a(n) = p^floor((n-1)/2)*(p+(p-2)*(-1)^n)/2.
a(n+3) = a(n+2)*a(n+1)/a(n). - Reinhard Zumkeller, Mar 04 2011
MATHEMATICA
RecurrenceTable[{a[1]==1, a[2]==4, a[n]==If[EvenQ[n], 4a[n-1], 5a[n-2]]}, a, {n, 30}] (* Harvey P. Dale, Jan 14 2013 *)
CROSSREFS
For the partial sums see A133629.
KEYWORD
nonn
AUTHOR
Hieronymus Fischer, Sep 19 2007
STATUS
approved