This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A061925 a(n) = ceiling(n^2/2) + 1. 16
 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)
 OFFSET 0,2 COMMENTS a(n+1) gives index of the first occurrence of n in A100795. - Amarnath Murthy, Dec 05 2004 First term in each group in A074148. - Amarnath Murthy, Aug 28 2002 LINKS Harry J. Smith, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (2,0,-2,1). FORMULA a(n) = a(n-1) + 2*floor((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 From R. J. Mathar, Feb 19 2010: (Start) 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). (End) a(n) = (2*n^2 - (-1)^n + 5)/4. - Bruno Berselli, Sep 29 2011 a(n) = A007590(n+1) - n + 1. - Wesley Ivan Hurt, Jul 15 2013 a(n) + a(n+1) = A027688(n). a(n+1) - a(n) = A109613(n). - R. J. Mathar, Jul 20 2013 MAPLE seq(floor((n^2+3)/2), n=0..25); # Gary Detlefs, Feb 13 2010 MATHEMATICA Table[Ceiling[n^2/2]+1, {n, 0, 60}] (* Vladimir Joseph Stephan Orlovsky, Apr 02 2011 *) PROG (PARI) { for (n=0, 1000, write("b061925.txt", n, " ", ceil(n^2/2) + 1) ) } \\ Harry J. Smith, Jul 29 2009 CROSSREFS Cf. A100795, A074147-A074149. Sequence in context: A127719 A074150 A261243 * A073736 A101593 A226893 Adjacent sequences:  A061922 A061923 A061924 * A061926 A061927 A061928 KEYWORD nonn,easy AUTHOR Henry Bottomley, May 17 2001 EXTENSIONS Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, Jun 09 2007 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 9 00:32 EST 2019. Contains 329871 sequences. (Running on oeis4.)