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Search: id:A051895
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| A051895 |
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Partial sums of second pentagonal numbers with even index (A049453). |
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+0
1
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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
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OFFSET
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0,2
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COMMENT
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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
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A. H. Beiler, Recreations in the Theory of Numbers, Dover, N.Y., 1964, pp. 194-196.
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FORMULA
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a(n)=n(n+1)(4n+3)/2.
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CROSSREFS
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Cf. A049453 and A017605.
Sequence in context: A024093 A110323 A060745 this_sequence A131211 A100855 A000605
Adjacent sequences: A051892 A051893 A051894 this_sequence A051896 A051897 A051898
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KEYWORD
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easy,nonn
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AUTHOR
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Barry E. Williams, Dec 17 1999
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