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%I #16 Jan 31 2020 13:15:57
%S 1,1,1,1,4,25,10201,1040606050201,17606710134796383100801078407630169,
%T 1397251576763829044923817239566095383950667477080314561212188721224520791793149263311589905001958916
%N a(0) = a(1) = a(2) = a(3) = 1; for n>3, a(n) = ( a(n-1)*a(n-2)*a(n-3) + 1 )^2 / a(n-4).
%H Seiichi Manyama, <a href="/A276268/b276268.txt">Table of n, a(n) for n = 0..11</a>
%F a(n) = A276267(n)^2.
%t RecurrenceTable[{a[n] == (a[n - 1] a[n - 2] a[n - 3] + 1)^2/a[n - 4], a[0] == a[1] == a[2] == a[3] == 1}, a, {n, 0, 10}] (* _Michael De Vlieger_, Aug 26 2016 *)
%t nxt[{a_,b_,c_,d_}]:={b,c,d,(b*c*d+1)^2/a}; NestList[nxt,{1,1,1,1},10][[All,1]] (* _Harvey P. Dale_, Jan 31 2020 *)
%o (Ruby)
%o def A(m, n)
%o a = Array.new(m, 1)
%o ary = [1]
%o while ary.size < n + 1
%o i = a[1..-1].inject(:*) + 1
%o i *= i
%o break if i % a[0] > 0
%o a = *a[1..-1], i / a[0]
%o ary << a[0]
%o end
%o ary
%o end
%o def A276268(n)
%o A(4, n)
%o end
%Y Cf. A081068, A276266, A276267.
%K nonn
%O 0,5
%A _Seiichi Manyama_, Aug 26 2016
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