A276126 - OEIS

%I #24 Aug 08 2022 18:52:07

%S 1,1,1,1,1,5,33,1281,1853441,3826997739521,2989151785658720873470945,

%T 271581474754155314350055167823358355425497243141,

%U 57581776430597685625970981157448022010386123824977761496513036956000541901241585948341716033

%N a(0) = a(1) = a(2) = a(3) = a(4) = 1; for n>4, a(n) = ( a(n-1)^2+a(n-2)^2+a(n-3)^2+a(n-4)^2+a(n-1)*a(n-2)*a(n-3)*a(n-4) ) / a(n-5).

%H Seiichi Manyama, <a href="/A276126/b276126.txt">Table of n, a(n) for n = 0..15</a>

%F a(n) = 10*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-1)*a(n-2)*a(n-3) - a(n-2)*a(n-3)*a(n-4) - a(n-3)*a(n-4)*a(n-1) - a(n-4)*a(n-1)*a(n-2) - a(n-5).

%t nxt[{a_,b_,c_,d_,e_}]:={b,c,d,e,(e^2+d^2+c^2+b^2+e*d*c*b)/a}; NestList[nxt,{1,1,1,1,1},15][[All,1]] (* _Harvey P. Dale_, Aug 08 2022 *)

%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(0){|s, i| s + i * i} + a[1..-1].inject(:*)

%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 A276126(n)

%o   A(5, n)

%o end

%Y Cf. A165903, A276124.

%K nonn

%O 0,6

%A _Seiichi Manyama_, Aug 21 2016