cp's OEIS Frontend

A276268 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).

%I A276268 #16 Jan 31 2020 13:15:57
%S A276268 1,1,1,1,4,25,10201,1040606050201,17606710134796383100801078407630169,
%T A276268 1397251576763829044923817239566095383950667477080314561212188721224520791793149263311589905001958916
%N A276268 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 A276268 Seiichi Manyama, <a href="/A276268/b276268.txt">Table of n, a(n) for n = 0..11</a>
%F A276268 a(n) = A276267(n)^2.
%t A276268 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 A276268 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 A276268 (Ruby)
%o A276268 def A(m, n)
%o A276268   a = Array.new(m, 1)
%o A276268   ary = [1]
%o A276268   while ary.size < n + 1
%o A276268     i = a[1..-1].inject(:*) + 1
%o A276268     i *= i
%o A276268     break if i % a[0] > 0
%o A276268     a = *a[1..-1], i / a[0]
%o A276268     ary << a[0]
%o A276268   end
%o A276268   ary
%o A276268 end
%o A276268 def A276268(n)
%o A276268   A(4, n)
%o A276268 end
%Y A276268 Cf. A081068, A276266, A276267.
%K A276268 nonn
%O A276268 0,5
%A A276268 _Seiichi Manyama_, Aug 26 2016