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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).
1
1, 1, 1, 1, 4, 25, 10201, 1040606050201, 17606710134796383100801078407630169, 1397251576763829044923817239566095383950667477080314561212188721224520791793149263311589905001958916
OFFSET
0,5
LINKS
FORMULA
a(n) = A276267(n)^2.
MATHEMATICA
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 *)
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 *)
PROG
(Ruby)
def A(m, n)
a = Array.new(m, 1)
ary = [1]
while ary.size < n + 1
i = a[1..-1].inject(:*) + 1
i *= i
break if i % a[0] > 0
a = *a[1..-1], i / a[0]
ary << a[0]
end
ary
end
def A276268(n)
A(4, n)
end
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Aug 26 2016
STATUS
approved