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A108261
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2nd order recursive series having the property that the product of any two adjacent terms is a triangular number, T(b) = b(b+1)/2 where b equals term a(n) of related series A108262.
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2
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2, 3, 12, 65, 374, 2175, 12672, 73853, 430442, 2508795, 14622324, 85225145, 496728542, 2895146103, 16874148072, 98349742325, 573224305874, 3340996092915, 19472752251612, 113495517416753, 661500352248902, 3855506596076655, 22471539224211024
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OFFSET
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0,1
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LINKS
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Kenneth J. Ramsey, Recursive Series Problem, digest of 4 messages in Triangular_and_Fibonacci_Numbers Yahoo group, May 28, 2005 - Mar 9, 2006. [Cached copy]
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FORMULA
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a(n) = 6*a(n-1) - a(n-2) - 4.
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MATHEMATICA
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RecurrenceTable[{a[0]==2, a[1]==3, a[n]==6a[n-1]-a[n-2]-4}, a, {n, 20}] (* Harvey P. Dale, Mar 19 2019 *)
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CROSSREFS
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KEYWORD
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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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