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A051895
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Partial sums of second pentagonal numbers with even index (A049453).
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2
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0, 7, 33, 90, 190, 345, 567, 868, 1260, 1755, 2365, 3102, 3978, 5005, 6195, 7560, 9112, 10863, 12825, 15010, 17430, 20097, 23023, 26220, 29700, 33475, 37557, 41958, 46690, 51765, 57195, 62992, 69168
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| For A049453(n+1), the corresponding formula would be: a(n)=(n+1)(6n+7) and its partial sums would be given by: a(n)=(n+1)(n+2)(4n+7)/2.
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REFERENCES
| A. H. Beiler, Recreations in the Theory of Numbers, Dover, N.Y., 1964, pp. 194-196.
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LINKS
| Index entries for sequences related to linear recurrences with constant coefficients, signature (4,-6,4,-1).
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FORMULA
| a(n) = n(n+1)(4n+3)/2.
G.f.: x*(7+5*x)/(1-x)^4. [Colin Barker, Jan 12 2012]
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MATHEMATICA
| Table[(n(4n-1)(n-1))/2, {n, 40}] (* From Harvey P. Dale, Mar 11 2011 *)
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CROSSREFS
| Cf. A049453 and A017605.
Sequence in context: A175189 A153286 A060745 * A168574 A131211 A100855
Adjacent sequences: A051892 A051893 A051894 * A051896 A051897 A051898
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KEYWORD
| nonn,easy
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AUTHOR
| Barry E. Williams, Dec 17 1999
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