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Search: id:A110349
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| A110349 |
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a(n) = n + (n+1) +(n-1) +(n+2) + (n-2) ... n terms. |
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+0
1
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| 1, 5, 9, 18, 25, 39, 49, 68, 81, 105, 121, 150, 169, 203, 225, 264, 289, 333, 361, 410, 441, 495, 529, 588, 625, 689, 729, 798, 841, 915, 961, 1040, 1089, 1173, 1225, 1314, 1369, 1463, 1521, 1620, 1681, 1785, 1849, 1958, 2025, 2139, 2209, 2328, 2401, 2525
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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Robert M. Ziff, "On Cardy's formula for the critical crossing probability in 2d percolation," J. Phys. A. 28, 1249-1255 (1995).
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FORMULA
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a(2n-1)=(2n-1)^2; a(2n)=4n^2+n. - Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 03 2005
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EXAMPLE
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a(4) = 4+5 +3 +6 = 18.
a(5) = 5+6+4 +7 +3 = 25.
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MAPLE
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a:=proc(n) if n mod 2 = 0 then n^2+n/2 else n^2 fi end: seq(a(n), n=1..60); (Deutsch)
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CROSSREFS
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Sequence in context: A062536 A099213 A061502 this_sequence A036832 A116453 A046578
Adjacent sequences: A110346 A110347 A110348 this_sequence A110350 A110351 A110352
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KEYWORD
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easy,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jul 21 2005
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 03 2005
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