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A061925
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Ceiling(n^2/2)+1.
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12
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1, 2, 3, 6, 9, 14, 19, 26, 33, 42, 51, 62, 73, 86, 99, 114, 129, 146, 163, 182, 201, 222, 243, 266, 289, 314, 339, 366, 393, 422, 451, 482, 513, 546, 579, 614, 649, 686, 723, 762, 801, 842, 883, 926, 969, 1014, 1059, 1106, 1153, 1202, 1251, 1302, 1353, 1406
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,2
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COMMENTS
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a(n+1) gives index of the first occurrence of n in A100795. - Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Dec 05 2004
First term in each group in A074148. - Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 28 2002
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LINKS
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Harry J. Smith, Table of n, a(n) for n=0..1000
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FORMULA
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a(n) = a(n-1)+2*[(n-1)/2]+1 = A061926(3, k) = 2*A002620(n+1)-(n-1) = A000982(n)+1. a(2n) = a(2n-1)+2n-1 = 2*n^2+1 = A058331(n); a(2n+1) = a(2n)+2n+1 = 2*(n^2+n+1) = A051890(n+1).
a(n) = floor((n^2+3)/2). - Gary Detlefs, Feb 13 2010
a(n) = 2*a(n-1) -2*a(n-3) +a(n-4). G.f.: (1-x^2+2*x^3)/((1+x) * (1-x)^3). - R. J. Mathar, Feb 19 2010
a(n) = (2*n^2-(-1)^n+5)/4. - Bruno Berselli, Sep 29 2011
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MAPLE
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seq(floor((n^2+3)/2), n=0..25); [From Gary Detlefs, Feb 13 2010]
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MATHEMATICA
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Table[Ceiling[n^2/2]+1, {n, 0, 60}] (*From Vladimir Joseph Stephan Orlovsky, Apr 02 2011*)
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PROG
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(PARI) { for (n=0, 1000, write("b061925.txt", n, " ", ceil(n^2/2) + 1) ) } [From Harry J. Smith, Jul 29 2009]
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CROSSREFS
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Cf. A100795, A074148.
Cf. A074147, A074148, A074149.
Sequence in context: A008823 A127719 A074150 * A073736 A101593 A084628
Adjacent sequences: A061922 A061923 A061924 * A061926 A061927 A061928
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KEYWORD
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nonn,easy
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AUTHOR
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Henry Bottomley, May 17 2001
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EXTENSIONS
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Edited by N. J. A. Sloane at the suggestion of Andrew Plewe, Jun 09 2007
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STATUS
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approved
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