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A076458
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Sum of numbers that can be written as t*n + u*(n+1) for nonnegative integers t,u in exactly five ways.
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2
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17, 165, 678, 1910, 4335, 8547, 15260, 25308, 39645, 59345, 85602, 119730, 163163, 217455, 284280, 365432, 462825, 578493, 714590, 873390, 1057287, 1268795, 1510548, 1785300, 2095925, 2445417, 2836890, 3273578, 3758835, 4296135, 4889072, 5541360
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OFFSET
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1,1
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REFERENCES
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Fred. Schuh, Vragen betreffende een onbepaalde vergelijking, Nieuw Tijdschrift voor Wiskunde, 52 (1964-1965) 193-198.
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LINKS
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FORMULA
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a(n) = n*(n+1)*(10*n^2+8*n-1)/2.
G.f.: x*(17+80*x+23*x^2)/(1-x)^5.
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MAPLE
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seq(1/2*n*(n+1)*(10*n^2+8*n-1), n=1..40);
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MATHEMATICA
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CoefficientList[Series[(17 + 80 x + 23 x^2)/(1 - x)^5, {x, 0, 50}], x] (* Vincenzo Librandi, Dec 30 2013 *)
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PROG
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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