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A276284
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a(0) = a(1) = a(2) = a(3) = a(4) = 1; for n > 4, a(n) = ( a(n-1)+a(n-3)+1 )*( a(n-2)+a(n-4)+1 ) / a(n-5).
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1
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1, 1, 1, 1, 1, 9, 33, 385, 13825, 5474305, 8430415841, 1398605982547209, 30625582893143965429313, 3098236789946633955987434183345281, 17332850039068891068793031113694107707268123637761
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listen;
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OFFSET
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0,6
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LINKS
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FORMULA
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a(n) = (8-4*(-1)^n)*a(n-1)*a(n-3) - a(n-2) - a(n-4) - 1 for n>3.
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MATHEMATICA
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RecurrenceTable[{a[n] == (a[n - 1] + a[n - 3] + 1) (a[n - 2] + a[n - 4] + 1)/a[n - 5], a[0] == a[1] == a[2] == a[3] == a[4] == 1}, a, {n, 0, 14}] (* Michael De Vlieger, Aug 27 2016 *)
nxt[{a_, b_, c_, d_, e_}]:={b, c, d, e, (e+c+1) (d+b+1)/a}; NestList[nxt, {1, 1, 1, 1, 1}, 15][[All, 1]] (* Harvey P. Dale, Dec 14 2021 *)
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PROG
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(Ruby)
def A(m, n)
a = Array.new(2 * m + 1, 1)
ary = [1]
while ary.size < n + 1
i = (1..m).inject(1){|s, i| s + a[2 * i - 1]} * (1..m).inject(1){|s, i| s + a[2 * i]}
break if i % a[0] > 0
a = *a[1..-1], i / a[0]
ary << a[0]
end
ary
end
A(2, n)
end
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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