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A011916
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((b(n)-1)+Sqrt(3*b(n)^2-4*b(n)+1))/2, where b(n) is A011922.
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3
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3, 44, 615, 8568, 119339, 1662180, 23151183, 322454384, 4491210195, 62554488348, 871271626679, 12135248285160, 169022204365563, 2354175612832724, 32789436375292575, 456697933641263328, 6360981634602394019
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Integers n such that n^2 = sum(n+1,n+2,n+3,...,n+x) for some value of x. 3 is a term because 3^2=9 and 4+5=9; 44 is a term because 44^2=1936 and the sum of (45,46,47,...,76) = 1936. [From Gil Broussard (gilbroussard(AT)bellsouth.net), Dec 23 2008]
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REFERENCES
| Mario VELUCCHI "Seeing couples" in Recreational and Educational Computing, to appear 1997.
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (15,-15,1). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 15 2010]
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FORMULA
| a(n) = +15*a(n-1) -15*a(n-2) +a(n-3). G.f.: x*(-3+x)/ ((x-1) * (x^2-14*x+1)). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 15 2010]
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CROSSREFS
| Sequence in context: A055539 A046946 A092545 * A193623 A102811 A142600
Adjacent sequences: A011913 A011914 A011915 * A011917 A011918 A011919
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KEYWORD
| nonn,easy
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AUTHOR
| Mario Velucchi (mathchess(AT)velucchi.it)
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EXTENSIONS
| More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 15 2010
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