The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A051936 Truncated triangular numbers: a(n) = n*(n+1)/2 - 9. 7
 1, 6, 12, 19, 27, 36, 46, 57, 69, 82, 96, 111, 127, 144, 162, 181, 201, 222, 244, 267, 291, 316, 342, 369, 397, 426, 456, 487, 519, 552, 586, 621, 657, 694, 732, 771, 811, 852, 894, 937, 981, 1026, 1072, 1119, 1167, 1216, 1266, 1317, 1369, 1422, 1476 (list; graph; refs; listen; history; text; internal format)
 OFFSET 4,2 COMMENTS Equals binomial transform of [1, 5, 1, 0, 0, 0, ...]. - Gary W. Adamson, Apr 30 2008 Numbers m > 0 such that 8m+73 is a square. - Bruce J. Nicholson, Jul 29 2017 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 4..10000 C. Rossiter, Depictions, Explorations and Formulas of the Euler/Pascal Cube [Dead link] C. Rossiter, Depictions, Explorations and Formulas of the Euler/Pascal Cube [Cached copy, May 15 2013] Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA G.f.: x^4*(-1-3*x+3*x^2) / (x-1)^3. a(n) = n + a(n-1) for n>4, a(4)=1. - Vincenzo Librandi, Aug 06 2010 a(n) = 2*A000217(n-3) - A000217(n-6), with A000217(-2)=1, A000217(-1)=0. - Bruno Berselli, Oct 13 2016 EXAMPLE Illustration of the initial terms:                                                           .                               .                         .   .       .                     .   .                     o   o   o     .   .                 o   o   o                 o   o   o   o   .   o   .             .   o   o   .             .   o   o   o   . .   .   .   .         .   .   o   .   .         .   .   o   o   .   . ----------------------------------------------------------------------       1                       6                           12 ---------------------------------------------------------------------- - Bruno Berselli, Oct 13 2016 MATHEMATICA Table[n*(n + 1)/2 - 9, {n, 4, 60}] (* Stefan Steinerberger, Mar 25 2006 *) k = 4; NestList[(k++; # + k) &, 1, 45] (* Robert G. Wilson v, Feb 02 2011 *) Drop[Accumulate[Range[60]]-9, 3] (* Harvey P. Dale, Jan 16 2012 *) PROG (Haskell) a051936 = (subtract 9) . a000217 a051936_list = scanl (+) 1 [5..] -- Reinhard Zumkeller, Oct 25 2012 (PARI) a(n)=n*(n+1)/2-9 \\ Charles R Greathouse IV, Oct 07 2015 CROSSREFS Cf. A000217. Sequence in context: A187391 A081846 A078816 * A215342 A146923 A256977 Adjacent sequences:  A051933 A051934 A051935 * A051937 A051938 A051939 KEYWORD nonn,nice,easy AUTHOR Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Dec 21 1999 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 May 6 13:04 EDT 2021. Contains 343585 sequences. (Running on oeis4.)