The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A098487 Triangle T(m,k) read by rows, where T(m,k) is the number of ways in which 1<=k<=m positions can be picked in an m X m square array such that all positions are mutually isolated. Two positions (s,t),(u,v) are considered as isolated from each other if min(abs(s-u),abs(t-v))>1. 12
 1, 4, 0, 9, 16, 8, 16, 78, 140, 79, 25, 228, 964, 1987, 1974, 36, 520, 3920, 16834, 42368, 62266, 49, 1020, 11860, 85275, 397014, 1220298, 2484382, 64, 1806, 29708, 317471, 2326320, 12033330, 44601420, 119138166, 81, 2968, 65240, 962089, 10087628, 77784658, 450193818, 1979541332, 6655170642 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For more information, links, programs see A098485. LINKS Alois P. Heinz, Rows n = 1..21, flattened EXAMPLE T(3,3) = a(6) = 8 because there are the following 8 ways to pick 3 positions isolated from each other from a 3 X 3 square array: X0X...X0X...X0X...X00...X00...0X0...00X...00X 000...000...000...00X...000...000...X00...000 X00...0X0...00X...X00...X0X...X0X...00X...X0X Triangle begins: : 1; : 4, 0; : 9, 16, 8; : 16, 78, 140, 79; : 25, 228, 964, 1987, 1974; : 36, 520, 3920, 16834, 42368, 62266; : 49, 1020, 11860, 85275, 397014, 1220298, 2484382; : 64, 1806, 29708, 317471, 2326320, 12033330, 44601420, 119138166; PROG See link in A098485. CROSSREFS A098485 gives selections where all marks are connected, A090642 gives total number of possible selections. Main diagonal gives A201513. Cf. A291716, A291717, A291718, A292152, A292153, A292154, A292155, A292156. Sequence in context: A187850 A186965 A330386 * A174381 A184363 A331451 Adjacent sequences: A098484 A098485 A098486 * A098488 A098489 A098490 KEYWORD nonn,tabl AUTHOR Hugo Pfoertner, Sep 15 2004 EXTENSIONS T(8,8) corrected by Alois P. Heinz, May 11 2017 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 November 28 08:48 EST 2022. Contains 358407 sequences. (Running on oeis4.)