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0, 1, 7, 52, 472, 5197, 67567, 1013512, 17229712, 327364537, 6874655287, 158117071612, 3952926790312, 106729023338437, 3095141676814687, 95949391981255312, 3166329935381425312, 110821547738349885937, 4100397266318945779687, 159915493386438885407812
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OFFSET
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0,3
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COMMENTS
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Also a(n) = floor(sqrt(A249348(n)*2)).
The positive terms are of the form 3k-2; this k (= 1, 3, 18, 157, ...) is the index of A249348(n) within the centered 9-gonal numbers A060544.
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LINKS
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FORMULA
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a(n) +(-2*n-3)*a(n-1) +(4*n-1)*a(n-2) +(-2*n+3)*a(n-3)=0. - R. J. Mathar, Oct 28 2014
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PROG
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(PARI) vector(10, n, A001147(n)\2) \\ To get the initial term a(0) for n=1.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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