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A133678
a(n)=6*a(n-1)+42*a(n-2) for n>=3, a(0)=1, a(1)=6, a(2)=72 .
1
1, 6, 72, 684, 7128, 71496, 728352, 7372944, 74828448, 758634336, 7694600832, 78030247104, 791354717568, 8025398683776, 81389290240512, 825402486161664, 8370765107071488, 84891495061218816, 860921104864315392, 8730969421757082624, 88544502934843742208
OFFSET
0,2
REFERENCES
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.
FORMULA
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
MATHEMATICA
Join[{1}, LinearRecurrence[{6, 42}, {6, 72}, 20]] (* Harvey P. Dale, Mar 25 2015 *)
CROSSREFS
Sequence in context: A281774 A036292 A061690 * A005548 A059410 A238103
KEYWORD
easy,nonn
AUTHOR
Philippe Deléham, Dec 31 2007
EXTENSIONS
Corrected and extended by Harvey P. Dale, Mar 25 2015
STATUS
approved