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%I A248049 #33 Oct 12 2022 15:21:36
%S A248049 2,1,1,1,2,6,24,240,3960,184800,33033000,26125799700,219429008298500,
%T A248049 31064340573760168675,206377779224083011749949745,
%U A248049 245390990689739612867279321757020455,230795626149641527446533813473152766756062242744
%N A248049 a(n) = (a(n-1) + a(n-2)) * (a(n-2) + a(n-3)) / a(n-4) with a(0) = 2, a(1) = a(2) = a(3) = 1.
%C A248049 It seems that degrees of factors when using [2,1,1,y] as initial condition are given by A233522. - _F. Chapoton_, May 21 2020
%C A248049 It seems also that degrees (w.r.t. x) of factors when using [2,1,x,y] as initial condition are given by A247907. - _F. Chapoton_, Jan 03 2021
%C A248049 Somos conjectures that log(a(n)) ~ 1.25255*c^n, where c = A060006. - _Bill McEachen_, Oct 11 2022
%H A248049 Robert Israel, <a href="/A248049/b248049.txt">Table of n, a(n) for n = 0..26</a>
%H A248049 Math Stack Exchange, <a href="https://math.stackexchange.com/questions/3586309/is-oeis-a248049-an-integer-sequence/4004892#4004892">Is OEIS A248049 an Integer Sequence</a>
%F A248049 a(n) = a(4-n) for all n in Z.
%F A248049 a(n) * a(n+4) = (a(n+1) + a(n+2)) * (a(n+2) + a(n+3)) for all n in Z.
%p A248049 a[0]:= 2: a[1]:= 1: a[2]:= 1: a[3]:= 1:
%p A248049 for n from 4 to 20 do
%p A248049 a[n] := (a[n-1] + a[n-2]) * (a[n-2] + a[n-3]) / a[n-4]
%p A248049 od:
%p A248049 seq(a[i],i=0..20); # _Robert Israel_, Mar 18 2020
%o A248049 (PARI) {a(n) = if( n<0, n=4-n); if( n<4, (n==0)+1, (a(n-1) + a(n-2)) * (a(n-2) + a(n-3)) / a(n-4))};
%Y A248049 Cf. A233522, A060006.
%K A248049 nonn
%O A248049 0,1
%A A248049 _Michael Somos_, Sep 30 2014

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