The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A131242 Partial sums of A059995: a(n) = sum_{k=0..n} floor(k/10). 18
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 33, 36, 39, 42, 45, 48, 51, 54, 57, 60, 64, 68, 72, 76, 80, 84, 88, 92, 96, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 156, 162, 168, 174, 180, 186, 192, 198 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,12 COMMENTS Complementary with A130488 regarding triangular numbers, in that A130488(n)+10*a(n)=n(n+1)/2=A000217(n). LINKS G. C. Greubel, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (2,-1,0,0,0,0,0,0,0,1,-2,1). FORMULA a(n) = (1/2)*floor(n/10)*(2n-8-10*floor(n/10)). a(n) = A059995(n)*(2n-8-10*A059995(n))/2. a(n) = (1/2)*A059995(n)*(n-8+A010879(n)). a(n) = (n-A010879(n))*(n+A010879(n)-8)/20. G.f.: x^10/((1-x^10)(1-x)^2). From Philippe Deléham, Mar 27 2013: (Start) a(10n) = A051624(n). a(10n+1) = A135706(n). a(10n+2) = A147874(n+1). a(10n+3) = 2*A005476(n). a(10n+4) = A033429(n). a(10n+5) = A202803(n). a(10n+6) = A168668(n). a(10n+7) = 2*A147875(n). a(10n+8) = A135705(n). a(10n+9) = A124080(n). (End) a(n) = A008728(n-10) for n>= 10. - Georg Fischer, Nov 03 2018 EXAMPLE As square array : 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 12, 14, 16, 18, 20, 22, 24, 26, 28, 30 33, 36, 39, 42, 45, 48, 51, 54, 57, 60 64, 68, 72, 76, 80, 84, 88, 92, 96, 100 105, 110, 115, 120, 125, 130, 135, 140, 145, 150 156, 162, 168, 174, 180, 186, 192, 198, 204, 210 ... - Philippe Deléham, Mar 27 2013 MATHEMATICA Table[(1/2)*Floor[n/10]*(2*n - 8 - 10*Floor[n/10]), {n, 0, 50}] (* G. C. Greubel, Dec 13 2016 *) Accumulate[Table[FromDigits[Most[IntegerDigits[n]]], {n, 0, 110}]] (* or *) LinearRecurrence[{2, -1, 0, 0, 0, 0, 0, 0, 0, 1, -2, 1}, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2}, 120] (* Harvey P. Dale, Apr 06 2017 *) PROG (PARI) for(n=0, 50, print1((1/2)*floor(n/10)*(2n-8-10*floor(n/10)), ", ")) \\ G. C. Greubel, Dec 13 2016 (PARI) a(n)=my(k=n\10); k*(n-5*k-4) \\ Charles R Greathouse IV, Dec 13 2016 CROSSREFS Cf. A008728, A059995, A010879, A002266, A130488, A000217, A002620, A130518, A130519, A130520, A174709, A174738, A118729, A218470. Sequence in context: A164836 A005358 A032518 * A008728 A179052 A083292 Adjacent sequences: A131239 A131240 A131241 * A131243 A131244 A131245 KEYWORD nonn,easy AUTHOR Hieronymus Fischer, Jun 21 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 18 11:53 EDT 2024. Contains 372630 sequences. (Running on oeis4.)