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A276259
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a(n) = 5*a(n-1)*a(n-2)*a(n-3) - a(n-4) with n>4, a(1) = a(2) = a(3) = a(4) = 1.
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3
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1, 1, 1, 1, 4, 19, 379, 144019, 5185404091, 1415179768826376436, 5284257989697826589787882104688841, 193886796198316302609610159795591363955441027433554915785933561
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OFFSET
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1,5
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LINKS
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FORMULA
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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 + 1) / a(n-4).
a(n)*a(n+1)*a(n+2)*a(n+3) = (a(n)^2 + a(n+1)^2 + a(n+2)^2 + a(n+3)^2 + 1)/5.
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MATHEMATICA
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RecurrenceTable[{a[n] == 5 a[n - 1] a[n - 2] a[n - 3] - a[n - 4], a[1] == a[2] == a[3] == a[4] == 1}, a, {n, 12}] (* Michael De Vlieger, Aug 26 2016 *)
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PROG
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(Ruby)
def A(m, n)
a = Array.new(m, 1)
ary = [1]
while ary.size < n
a = *a[1..-1], *a[1..-1].inject(:*) * (m + 1) - a[0]
ary << a[0]
end
ary
end
A(4, 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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