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A133678
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a(n)=6*a(n-1)+42*a(n-2) for n>=3, a(0)=1, a(1)=6, a(2)=72 .
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1
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1, 6, 72, 684, 7128, 71496, 728352, 7372944, 74828448, 758634336, 7694600832, 78030247104, 791354717568, 8025398683776, 81389290240512, 825402486161664, 8370765107071488, 84891495061218816, 860921104864315392, 8730969421757082624, 88544502934843742208
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OFFSET
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0,2
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REFERENCES
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D. A. Cox, Primes of the form x^2+ny^2, Wiley, New York, 1989.
D. E. Flath, Introduction to Number Theory, Wiley-Interscience, 1989.
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LINKS
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FORMULA
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G.f.: (1-6*x^2)/(1-6*x-42*x^2) . a(n) = Sum_{k, 0<=k<=n}A122950(n,k)*6^k .
a(1)=6, a(2)=72, a(n)=6*a(n-1)+42*a (n-2). - Harvey P. Dale, Mar 25 2015
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MATHEMATICA
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Join[{1}, LinearRecurrence[{6, 42}, {6, 72}, 20]] (* Harvey P. Dale, Mar 25 2015 *)
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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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EXTENSIONS
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STATUS
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approved
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