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A030280
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COMPOSE triangular numbers with triangular numbers.
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5
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1, 6, 30, 137, 588, 2415, 9600, 37209, 141336, 528049, 1945800, 7086555, 25550547, 91319973, 323890062, 1140985116, 3995155506, 13913280006, 48216776266, 166355744244, 571636515369, 1957015021744, 6677155551312
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OFFSET
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1,2
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LINKS
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FORMULA
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G.f.: [(1-x)^6]/[(1-4x+3x^2-x^3)^3].
a(1)=1, a(2)=6, a(3)=30, a(4)=137, a(5)=588, a(6)=2415, a(7)=9600, a(8)=37209, a(9)=141336, a(n)=12*a(n-1)-57*a(n-2)+139*a(n-3)- 195*a(n-4)+ 174*a(n-5)-102*a(n-6)+39*a(n-7)-9*a(n-8)+a(n-9). - Harvey P. Dale, Jan 08 2013
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MATHEMATICA
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CoefficientList[Series[((1-x)^6)/((1-4x+3x^2-x^3)^3), {x, 0, 30}], x] (* or *) LinearRecurrence[{12, -57, 139, -195, 174, -102, 39, -9, 1}, {1, 6, 30, 137, 588, 2415, 9600, 37209, 141336}, 30] (* Harvey P. Dale, Jan 08 2013 *)
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CROSSREFS
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KEYWORD
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nonn,nice,easy
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AUTHOR
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STATUS
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approved
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