A108176 - OEIS

A108176

a(1) = 1, a(n) = (Sum_{k=1..floor(n/2)} 1/a(n + 1 - 2k))*(Product_{k=1..floor(n/2)} a(n + 1 - 2k)).

1, 1, 1, 2, 3, 7, 23, 164, 3786, 620973, 2351006074, 1459911295051236, 3432260322166663402961472, 5010795611887306064313121202903094714708, 17198354961167628388233455836547370709483687001035342768448084064

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OFFSET

1,4

LINKS

Table of n, a(n) for n=1..15.

FORMULA

For n >= 2, a(n+4) = a(n+1)*(a(n+2) - a(n)a(n+1)) + a(n+2)a(n+3).

MAPLE

a[1]:=1: for n from 2 to 25 do a[n]:=sum(1/a[n+1-2*j], j=1..floor(n/2))*product(a[n+1-2*k], k=1..floor(n/2)) od: seq(a[n], n=1..16); # Emeric Deutsch, Jun 14 2005

MATHEMATICA

a[1] = 1; a[n_] := a[n] = Sum[1/a[n + 1 - 2k], {k, Floor[n/2]}] Product[ a[n + 1 - 2k], {k, Floor[n/2]}]; Table[ a[n], {n, 15}] (* Robert G. Wilson v, Jun 14 2005 *)

CROSSREFS

Cf. A057438.

Sequence in context: A281529 A090253 A001064 * A111235 A066356 A006892

Adjacent sequences: A108173 A108174 A108175 * A108177 A108178 A108179

KEYWORD

nonn

AUTHOR

Leroy Quet, Jun 13 2005

EXTENSIONS

More terms from Robert G. Wilson v and Emeric Deutsch, Jun 14 2005

STATUS

approved