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A083697 2^(2^n-1) * Fibonacci(2^n). 1
1, 2, 24, 2688, 32342016, 4677882957791232, 97861912906883207538212742365184, 42829440312913272520181533609472356498655100482256687829780267008 (list; graph; refs; listen; history; internal format)
OFFSET

0,2

COMMENTS

A083696(n)/a(n) converges to sqrt(5). a(n)=2*a(n-1)*A083696(n-1). Similar to A081460: a(n) is the denominator of the same mapping f(r)=(1/2)(r+5/r) but with initial value r=1.

FORMULA

a(n)=Sum[Prod(2^n-k), (k=0, 2r)]5^r/(2r+1)!, (r=0, 2^n-1).

MATHEMATICA

Table[Sum[Product[2^n - k, {k, 0, 2*r}]k^r/(2*r + 1)!, {r, 0, 2^n - 1}], {n, 0, 8}]

CROSSREFS

Equals A058635(n) * A058891(n).

Sequence in context: A053995 A184595 A007079 * A110131 A112332 A101339

Adjacent sequences:  A083694 A083695 A083696 * A083698 A083699 A083700

KEYWORD

easy,nonn

AUTHOR

Mario Catalani (mario.catalani(AT)unito.it), May 22 2003

EXTENSIONS

The next term is too large to include.

Better description from Ralf Stephan, Aug 29 2004

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Last modified February 15 05:45 EST 2012. Contains 205694 sequences.