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1, 4, 11, 25, 50, 93, 162, 272, 439, 694, 1069, 1627, 2432, 3611, 5292, 7730, 11181, 16156, 23167, 33237, 47390, 67673, 96134, 136868, 193971, 275634, 390049, 553599, 782668, 1110023, 1568432, 2223430, 3140553, 4450872, 6285459, 8906457, 12576010, 17818405
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OFFSET
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1,2
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LINKS
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Table of n, a(n) for n=1..38.
Index to sequences with linear recurrences with constant coefficients, signature (3,0,-8,7,3,-6,2).
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FORMULA
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a(n) = Sum_{i=1..n} 1/8*(2^(i/2+2)*((10-7*sqrt(2))*(-1)^(i)+10+7*sqrt(2))-(-1)^(i)-2*i*(i+12)-79)
G.f.: (1+x-x^2)/((1-x)^4*(1+x)*(1-2*x^2)) [Alexander R. Povolotsky, Aug 12 2011]
a(n)=1/32*((-1/2)^n+32*(41*sqrt(2)-58)*(sqrt(2)-2)^n-32*(58+41*sqrt(2))* (-2-sqrt(2))^n)
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EXAMPLE
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We have A193911(1)=1, A193911(2)=3, and A193911(3)=7. Thus a(1)=1, a(2)=4, and a(3)=11.
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CROSSREFS
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Sequence in context: A036837 A215052 A011851 * A136395 A014160 A014162
Adjacent sequences: A193909 A193910 A193911 * A193913 A193914 A193915
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KEYWORD
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nonn
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AUTHOR
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Jeffrey R. Goodwin, Aug 08 2011
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STATUS
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approved
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