The OEIS is supported by the many generous donors to the OEIS Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A160125 Number of squares and rectangles that are created at the n-th stage in the toothpick structure (see A139250). 9
 0, 0, 2, 2, 0, 4, 10, 6, 0, 4, 8, 4, 4, 20, 30, 14, 0, 4, 8, 4, 4, 20, 28, 12, 4, 16, 20, 12, 28, 72, 78, 30, 0, 4, 8, 4, 4, 20, 28, 12, 4, 16, 20, 12, 28, 72, 76, 28, 4, 16, 20, 12, 28, 68, 68, 28, 24, 52, 52, 52, 128, 224, 190, 62, 0, 4, 8, 4, 4, 20, 28, 12, 4, 16, 20, 12, 28, 72 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.] N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS FORMULA See Maple program for recurrence. MAPLE # First construct A168131: w := proc(n) option remember; local k, i; if (n=0) then RETURN(0) elif (n <= 3) then RETURN(n-1) else k:=floor(log(n)/log(2)); i:=n-2^k; if (i=0) then RETURN(2^(k-1)-1) elif (i<2^k-2) then RETURN(2*w(i)+w(i+1)); elif (i=2^k-2) then RETURN(2*w(i)+w(i+1)+1); else RETURN(2*w(i)+w(i+1)+2); fi; fi; end; # Then construct A160125: r := proc(n) option remember; local k, i; if (n<=2) then RETURN(0) elif (n <= 4) then RETURN(2) else k:=floor(log(n)/log(2)); i:=n-2^k; if (i=0) then RETURN(2^k-2) elif (i<=2^k-2) then RETURN(4*w(i)); else RETURN(4*w(i)+2); fi; fi; end; [seq(r(n), n=0..200)]; # N. J. A. Sloane, Feb 01 2010 MATHEMATICA w [n_] := w[n] = Module[{k, i}, Which[n == 0, 0, n <= 3, n - 1, True, k = Floor[Log[2, n]]; i = n - 2^k; Which[i == 0, 2^(k - 1) - 1, i < 2^k - 2, 2 w[i] + w[i + 1], i == 2^k - 2, 2 w[i] + w[i + 1] + 1, True, 2 w[i] + w[i + 1] + 2]]]; r[n_] := r[n] = Module[{k, i}, Which[n <= 2, 0, n <= 4, 2, True, k = Floor[Log[2, n]]; i = n - 2^k; Which[i == 0, 2^k - 2, i <= 2^k - 2, 4 w[i], True, 4 w[i] + 2]]]; Array[r, 78] (* Jean-François Alcover, Apr 15 2020, from Maple *) CROSSREFS First differences of A160124. Cf. toothpick sequence A139250. Cf. A159786, A159787, A159788, A159789, A160124, A160126, A160127. Sequence in context: A009545 A084102 A221609 * A151868 A344913 A052079 Adjacent sequences:  A160122 A160123 A160124 * A160126 A160127 A160128 KEYWORD nonn AUTHOR Omar E. Pol, May 03 2009 EXTENSIONS Terms beyond a(10) from R. J. Mathar, Jan 21 2010 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 October 3 22:17 EDT 2022. Contains 357237 sequences. (Running on oeis4.)