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A072287 Let f(n, m) = binomial(n - m/2 + 1, n - m + 1) - binomial(n - m/2, n - m + 1) and let s(n) = Sum_{k=0..n} f(n, k); then a(n) = numerator of s(n). 1
1, 2, 7, 47, 155, 2027, 6597, 42835, 138875, 3599155, 11654465, 75457289, 244238477, 3161900479, 10232916665, 66231885067, 214336798299, 11097918730051, 35913975952793, 232441522435405, 752199270651129 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..20.

FORMULA

s(0)=1, s(1)=2, s(n+1)=s(n)+s(n-1)+binomial(n-1/2, n) for n>=1.

EXAMPLE

1,2,7/2,47/8,155/16,2027/128,6597/256,42835/1024,138875/2048,...

MATHEMATICA

f[n_, m_] := Binomial[n - m/2 + 1, n - m + 1] - Binomial[n - m/2, n - m + 1]; s[n_] := Sum[ f[n, k], {k, 0, n}]; Table [Numerator[s[n]], {n, 0, 26}]

CROSSREFS

Denominator of s(n+1) = A046161(n).

Sequence in context: A116892 A201481 A054555 * A290488 A276649 A091117

Adjacent sequences:  A072284 A072285 A072286 * A072288 A072289 A072290

KEYWORD

nonn,easy,frac

AUTHOR

Michele Dondi (bik.mido(AT)tiscalinet.it), Jul 11 2002

STATUS

approved

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Last modified October 20 00:55 EDT 2018. Contains 316378 sequences. (Running on oeis4.)