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Search: id:A062027
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| A062027 |
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a(1) = a(2) = a(3) = 1; and for n>3 a(n) = 1*2*3*4 + 2*3*4*5 + 3*4*5*6 + ... + (n-1)*n*1*2 + n*1*2*3, the sum of the cyclic product of terms taken four at a time, final term being n*1*2*3 = 6n. |
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+0
2
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| 1, 1, 1, 96, 274, 720, 1680, 3520, 6750, 12048, 20284, 32544, 50154, 74704, 108072, 152448, 210358, 284688, 378708, 496096, 640962, 817872, 1031872, 1288512, 1593870, 1954576, 2377836, 2871456, 3443866, 4104144, 4862040, 5728000
(list; graph; listen)
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OFFSET
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1,4
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LINKS
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Harry J. Smith, Table of n, a(n) for n=1,...,1000
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FORMULA
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a(n) = (n+1)(n)(n-1)(n-2)(n-3)/5 + n(n^2 -n +6).
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EXAMPLE
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a(5) = 1*2*3*4 + 2*3*4*5 + 3*4*5*1 + 4*5*1*2 + 5*1*2*3 = 274.
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PROGRAM
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(PARI) { a=1; for (n=1, 1000, if (n>3, a=(n + 1)*n*(n - 1)*(n - 2)*(n - 3)/5 + n*(n^2 - n + 6)); write("b062027.txt", n, " ", a) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jul 30 2009]
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CROSSREFS
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Sequence in context: A108609 A125511 A124106 this_sequence A048189 A084048 A051483
Adjacent sequences: A062024 A062025 A062026 this_sequence A062028 A062029 A062030
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jun 02 2001
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EXTENSIONS
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More terms from Jason Earls (zevi_35711(AT)yahoo.com), Jun 07 2001
Term a(4) corrected by Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jul 30 2009
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