A276267 a(n) = ( a(n-1)^2*a(n-2)^2*a(n-3)^2 + 1 ) / a(n-4), with a(0)=a(1)=a(2)=a(3)=1.

1, 1, 1, 1, 2, 5, 101, 1020101, 132690278976255013, 37379828474243017116309068570169440106423243719554

Offset

0,5

Links

Seiichi Manyama, Table of n, a(n) for n = 0..11

Mathematica

RecurrenceTable[{a[n] == (a[n - 1]^2 a[n - 2]^2 a[n - 3]^2 + 1)/a[n - 4], a[0] == a[1] == a[2] == a[3] == 1}, a, {n, 0, 10}] (* Michael De Vlieger, Aug 26 2016 *)
nxt[{a_, b_, c_, d_}]:={b, c, d, (b^2 c^2 d^2+1)/a}; NestList[nxt, {1, 1, 1, 1}, 10][[All, 1]] (* Harvey P. Dale, Nov 18 2021 *)

Prog

(Ruby)
def A(m, n)
  a = Array.new(m, 1)
  ary = [1]
  while ary.size < n + 1
    i = (a[1..-1].inject(:*)) ** 2 + 1
    break if i % a[0] > 0
    a = *a[1..-1], i / a[0]
    ary << a[0]
  end
  ary
end
def A276267(n)
  A(4, n)
end

Crossrefs

Cf. A001519, A208209.

Sequence in context: A027720 A132482 A208209 * A215845 A276110 A136106

Adjacent sequences: A276264 A276265 A276266 * A276268 A276269 A276270

Keyword

nonn

Author

Seiichi Manyama, Aug 26 2016

Status

approved