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%I #8 Oct 30 2018 09:43:45
%S 1,1,1,3,3,9,81,99,649539,649737,274124633198656977,
%T 274124633199956451,
%U 20598907656583661830059012023854018733151994905840579,20598907656583661830059012023854019281401261305753481
%N Alternately form product and sum of all previous terms.
%C Note that definition does not make a(1) a special case; it is the empty product, which is 1. If we started with addition, the sequence would be all zeros.
%H Iain Fox, <a href="/A122961/b122961.txt">Table of n, a(n) for n = 1..18</a>
%H Iain Fox, <a href="/A122961/a122961.txt">Table of n, a(n) for n = 1..34</a>
%F a(1) = a(2) = 1. For n > 1, a(2n-1) = a(2n-3)^2 * a(2n-2), a(2n) = 2 * a(2n-2) + a(2n-1).
%o (PARI) first(n) = my(res = vector(n, i, 1)); for(x=4, n, res[x]=if(x%2, prod(i=1, x-1, res[i]), sum(i=1, x-1, res[i]))); res \\ _Iain Fox_, Oct 29 2018
%o (PARI) first(n) = my(res = vector(n, i, 1)); for(x=4, n, res[x]=if(x%2, res[x-1]*res[x-2]^2, res[x-1]+2*res[x-2])); res \\ _Iain Fox_, Oct 29 2018
%Y Cf. A039941, A000004, A320603.
%K nonn
%O 1,4
%A _Franklin T. Adams-Watters_, Oct 26 2006
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