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0, 0, 21, 364, 2730, 13020, 46655, 137256, 349524, 797160, 1666665, 3247860, 5971966, 10458084, 17568915, 28476560, 44739240, 68389776, 102036669, 148978620, 213333330, 300181420, 415726311, 567470904, 764411900, 1017252600
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refs;
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history;
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OFFSET
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0,3
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COMMENTS
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Also integer sequences for (n^2-n)/1 (A002378 offset), (n^3-n)/2 (A027480 offset), (n^43-n)/42 (A108496) and (n^1807-n)/1806.
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 0..1000
D. Zagier, Problems posed at the St Andrews Colloquium, 1996.
Index to sequences with linear recurrences with constant coefficients, signature (8,-28,56,-70,56,-28,8,-1).
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FORMULA
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a(n) =(n-1)*A059721(n) =-A024004(n)*n/6.
G.f.: 7*x^2*(3+28*x+58*x^2+28*x^3+3*x^4)/(1-x)^8. [Colin Barker, May 08 2012]
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EXAMPLE
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a(2) = (2^7-2)/6 = 126/6 = 21.
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PROG
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(MAGMA) [(n^7-n)/6: n in [0..40]]; // Vincenzo Librandi, May 02 2011
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CROSSREFS
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Cf. A014117, A108497, A108499.
Sequence in context: A006105 A167032 A051564 * A178351 A152182 A036904
Adjacent sequences: A108492 A108493 A108494 * A108496 A108497 A108498
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KEYWORD
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nonn,easy
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AUTHOR
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Henry Bottomley, Jun 06 2005
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STATUS
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approved
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