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%I #9 Oct 10 2019 11:28:36
%S 1,1,1,1,2,4,6,15,35,119,221,1703,31571,444163,62571693,16130221953,
%T 31653658032799,1139752929797333269,190765682365696256860989,
%U 13391304481955883169111997465697
%N a(n) = denominator of b(n), where b(1) = 1, b(n+1) = (sum{k=1 to n} b(k))/product{j=1 to n} b(j).
%F For n >= 4, b(n) = 1 +(b(n-1)-1)/b(n-2).
%t f[l_List] := Append[l, Plus @@ l/Times @@ l];Denominator[Nest[f, {1}, 20]] (* _Ray Chandler_, Feb 13 2007 *)
%Y Cf. A127678.
%K easy,frac,nonn
%O 1,5
%A _Leroy Quet_, Jan 23 2007
%E Extended by _Ray Chandler_, Feb 13 2007
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