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A069944
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Let b(1)=b(2)=1, b(n+2)=(1/(n+1))*(b(n+1)+b(n)); then a(n)=denominator(b(n)).
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2
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1, 1, 1, 3, 12, 60, 180, 630, 10080, 18144, 453600, 2494800, 59875200, 778377600, 1089728640, 40864824000, 1307674368000, 22230464256000, 15390321408000, 380140938777600, 76028187755520000, 1596591942865920000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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COMMENTS
| Sum(k=1,infinity,b(k))=e^(3/2) where e=2,718... More generally if b(1)=b(2)=...=b(m)=1 and b(n+m+1)=1/(n+m)*(b(n+m)+b(n+m-1)+...+b(n)) then Sum(k=1,infinity,b(k))=e^H(m) where H(m)=1+1/2+1/3+...+1/m is the m-th harmonic number (Benoit Cloitre and Boris Gourevitch).
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CROSSREFS
| Cf. A069943.
A069943(n)/a(n) = A000085(n-1)/A000142(n-1) in lowest terms. (Christian G. Bower, Jan 14 2006).
Sequence in context: A114419 A090830 A127918 * A073996 A003483 A128602
Adjacent sequences: A069941 A069942 A069943 * A069945 A069946 A069947
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KEYWORD
| easy,frac,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 27 2002
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