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A160790
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Vertex number of a rectangular spiral. The first differences (A160791) are the edge lengths of the spiral. The distances between two nearest edges, that are parallel to the initial edge, are the natural numbers.
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5
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0, 1, 2, 4, 7, 10, 16, 20, 30, 35, 50, 56, 77, 84, 112, 120, 156, 165, 210, 220, 275, 286, 352, 364, 442, 455, 546, 560, 665, 680, 800, 816, 952, 969, 1122, 1140, 1311, 1330, 1520, 1540, 1750, 1771, 2002, 2024, 2277, 2300, 2576, 2600, 2900, 2925, 3250, 3276, 3627, 3654, 4032, 4060, 4466, 4495, 4930, 4960, 5425
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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LINKS
| Nathaniel Johnston, Table of n, a(n) for n = 0..5000
Index to sequences with linear recurrences with constant coefficients, signature (1,3,-3,-3,3,1,-1).
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FORMULA
| a(n)= +a(n-1) +3*a(n-2) -3*a(n-3) -3*a(n-4) +3*a(n-5) +a(n-6) -a(n-7).
G.f.: -x*(-1-x+x^2) / ( (1+x)^3*(x-1)^4 ).
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MAPLE
| A160791 := proc(n) if type(n, 'odd') then ceil(n/2) ; else A000217(n/2) ; end if; end proc:
A160790 := proc(n) if n = 0 then 0; else add(A160791(i), i=0..n) ; end if; end proc:
seq(A160790(n), n=0..60) ;
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CROSSREFS
| Cf. A160791, A160792.
Sequence in context: A024668 A188951 A176099 * A173726 A000376 A000375
Adjacent sequences: A160787 A160788 A160789 * A160791 A160792 A160793
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KEYWORD
| easy,nonn
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AUTHOR
| Omar E. Pol (info(AT)polprimos.com), May 29 2009
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EXTENSIONS
| Edited by Omar E. Pol (info(AT)polprimos.com), Feb 08 2010
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