This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A131218 Gray code/ Silvester-Hadamard binary triangular sequence from 16 X 16 self-similar matrix. 2
 1, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 0, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This algorithm gives a real Gray code binary triangular sequence. See A140820 for another version. LINKS FORMULA a(n,m) = Antidiagonal[HadamardMatrix[n,m]] EXAMPLE {1}, {1, 1}, {1, 0, 1}, {1, 0, 0, 1}, {1, 1, 0, 1, 1}, {1, 1, 0, 0, 1, 1}, {1, 0, 0, 0, 0, 0, 1}, {1, 0, 0, 0, 0, 0, 0, 1}, {1, 1, 0, 0, 0, 0, 0, 1, 1}, {1, 1, 1, 1, 0, 0, 1, 1, 1, 1}, {1, 0, 1, 1, 0, 0, 0, 1, 1, 0, 1}, {1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1}, {1, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 1}, {1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1}, {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}, {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1} MATHEMATICA Clear[c, b, n, a0] c[i_, k_]:=Floor[Mod[i/2^k, 2]]; b[i_, k_]=If[c[i, k]==0&&c[i, k+1]\[Equal]0, 0, If[c[ i, k]==1&&c[i, k+1]\[Equal]1, 0, 1]]; a0=Table[If[Sum[b[i, k]*b[j, k], {k, 0, n}]\[Equal]0, 1, 0], {j, 0, n}, {i, 0, n}]; ListDensityPlot[a0, Mesh\[Rule]False]; c=Delete[Table[Reverse[Table[a0[[n, l-n]], {n, 1, l-1}]], {l, 1, Dimensions[a0][[1]]+1}], 1]; Flatten[c] CROSSREFS Cf. A121801, A122944, A123949, A140820. Sequence in context: A154957 A140865 A114000 * A174391 A113998 A253084 Adjacent sequences:  A131215 A131216 A131217 * A131219 A131220 A131221 KEYWORD nonn,uned,tabl,obsc AUTHOR Roger L. Bagula, Sep 27 2007 EXTENSIONS This looks interesting, but I do not understand the definition. - N. J. A. Sloane, Oct 16 2008 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 June 16 13:37 EDT 2019. Contains 324152 sequences. (Running on oeis4.)