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A112958
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a(1) = a(2) = a(3) = a(4) = 1; for n>1: a(n+4) = a(n)^2 + a(n+1)^2 + a(n+2)^2 + a(n+3)^2.
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6
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1, 1, 1, 1, 4, 19, 379, 144019, 20741616379, 430214650034342688004, 185084645104171955001009752069374428191659
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OFFSET
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1,5
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COMMENTS
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A quadratic tetranacci sequence.
This is to A000283 as a tetranacci (A000288) is to Fibonacci. Primes in this begin 19, 379.
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LINKS
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EXAMPLE
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1^2 + 4^2 + 19^2 + 379^2 = 144019.
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MATHEMATICA
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RecurrenceTable[{a[1] == a[2] == a[3] == a[4] == 1, a[n] == a[n-1]^2 + a[n-2]^2 + a[n-3]^2 + a[n-4]^2}, a, {n, 15}] (* Vincenzo Librandi, Aug 21 2016 *)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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