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Search: id:A055099
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| 1, 4, 14, 50, 178, 634, 2258, 8042, 28642, 102010, 363314, 1293962, 4608514, 16413466, 58457426, 208199210, 741512482, 2640935866, 9405832562, 33499369418, 119309773378, 424928058970, 1513403723666, 5390067288938
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OFFSET
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0,2
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REFERENCES
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I. P. Goulden and D. M. Jackson, Combinatorial Enumeration, Wiley, N.Y., 1983,(Problem 2.4.6).
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FORMULA
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G.f.: (1+x)/(1-3*x-2*x^2).
a(n)=a*c^n-b*d^n, a := (5+sqrt(17))/(2*sqrt(17)), b := (5-sqrt(17))/(2*sqrt(17)), c := (3+sqrt(17))/2, d := (3-sqrt(17))/2.
a(n)= sum(A054458(n, m), m=0..n). a(n)= F32(n)+F32(n-1) with F32(n)=A007482(n), n >= 1, a(0)=1.
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CROSSREFS
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Cf. A054458, A007482, A002203.
Sequence in context: A026630 A034459 A120747 this_sequence A047008 A047065 A055990
Adjacent sequences: A055096 A055097 A055098 this_sequence A055100 A055101 A055102
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KEYWORD
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easy,nonn
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AUTHOR
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Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de), Apr 26 2000
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