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A001509
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a(n) = (5*n + 1)*(5*n + 2)*(5*n + 3).
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1
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6, 336, 1716, 4896, 10626, 19656, 32736, 50616, 74046, 103776, 140556, 185136, 238266, 300696, 373176, 456456, 551286, 658416, 778596, 912576, 1061106, 1224936, 1404816, 1601496, 1815726, 2048256, 2299836, 2571216, 2863146, 3176376, 3511656, 3869736, 4251366
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OFFSET
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0,1
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LINKS
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FORMULA
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G.f.: 6*(1 + 52*x + 68*x^2 + 4*x^3)/(1 - x)^4. - Stefano Spezia, Jan 03 2023
Sum_{n>=0} 1/a(n) = sqrt(2*(25-11*sqrt(5))/5)*Pi/20 + log(phi)/(2*sqrt(5)), where phi is the golden ratio (A001622). - Amiram Eldar, Jan 26 2023
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MAPLE
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MATHEMATICA
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Table[(5*n + 1)*(5*n + 2)*(5*n + 3), {n, 0, 100}] (* Harvey P. Dale, Apr 21 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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