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A099392
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Floor[(n^2-2*n+3)/2].
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4
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1, 1, 3, 5, 9, 13, 19, 25, 33, 41, 51, 61, 73, 85, 99, 113, 129, 145, 163, 181, 201, 221, 243, 265, 289, 313, 339, 365, 393, 421, 451, 481, 513, 545, 579, 613, 649, 685, 723, 761, 801, 841, 883, 925, 969, 1013, 1059, 1105, 1153, 1201, 1251, 1301, 1353, 1405
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (2,0,-2,1).
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FORMULA
| a(n)=ceiling(n^2/2)-n+1. - Paul Barry (pbarry(AT)wit.ie), Jul 16 2006; index shifted by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 29 2007
a(n+1) = ceiling( A002522(n)/2) . - Branko Curgus (curgus(AT)cc.wwu.edu), Sep 02 2007
G.f. x *( -1+x-x^2-x^3 ) / ( (1+x)*(x-1)^3 ). a(n)= +2*a(n-1) -2*a(n-3) +a(n-4). a(n+1) = (3+2*n^2+(-1)^n)/4. - R. J. Mathar, Feb 20 2011
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CROSSREFS
| Differs from A085913 at n = 61. Apart from leading term, identical to A080827.
Sequence in context: A207187 A065802 A118028 * A080827 A102378 A118026
Adjacent sequences: A099389 A099390 A099391 * A099393 A099394 A099395
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KEYWORD
| nonn
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AUTHOR
| Ralf Stephan following a suggestion from Luke Pebody, Oct 20 2004
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