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A001546
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a(n) = (8*n+1)*(8*n+3)*(8*n+5)*(8*n+7).
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1
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105, 19305, 156009, 606825, 1666665, 3728745, 7284585, 12924009, 21335145, 33304425, 49716585, 71554665, 99900009, 135932265, 180929385, 236267625, 303421545, 383964009, 479566185, 591997545, 723125865, 874917225, 1049436009, 1248844905, 1475404905
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OFFSET
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0,1
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COMMENTS
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3 divides a(n).
Sum_{k>=0} 1/a(k) = Pi/(96*(2+sqrt(2))) = 0.0095849081719... [Jolley eq. 243] (End)
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REFERENCES
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Jolley, Summation of Series, Dover (1961).
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LINKS
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FORMULA
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G.f.: -3*(35+6260*x+20178*x^2+6260*x^3+35*x^4)/(x-1)^5. [Maksym Voznyy (voznyy(AT)mail.ru), Jul 27 2009]
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n > 4. - Wesley Ivan Hurt, Jan 02 2017
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MAPLE
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MATHEMATICA
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Table[Times@@(8n + {1, 3, 5, 7}), {n, 0, 30}] (* Harvey P. Dale, Jan 09 2011 *)
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PROG
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(Magma) [(8*n+1)*(8*n+3)*(8*n+5)*(8*n+7): n in [0..20]]; // Vincenzo Librandi, Oct 04 2011
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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