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 A147582 First differences of A147562. 54
 1, 4, 4, 12, 4, 12, 12, 36, 4, 12, 12, 36, 12, 36, 36, 108, 4, 12, 12, 36, 12, 36, 36, 108, 12, 36, 36, 108, 36, 108, 108, 324, 4, 12, 12, 36, 12, 36, 36, 108, 12, 36, 36, 108, 36, 108, 108, 324, 12, 36, 36, 108, 36, 108, 108, 324, 36, 108, 108, 324, 108, 324, 324, 972, 4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Bisection of A323651. - Omar E. Pol, Mar 04 2019 REFERENCES D. Singmaster, On the cellular automaton of Ulam and Warburton, M500 Magazine of the Open University, #195 (December 2003), pp. 2-7. S. Ulam, On some mathematical problems connected with patterns of growth of figures, pp. 215-224 of R. E. Bellman, ed., Mathematical Problems in the Biological Sciences, Proc. Sympos. Applied Math., Vol. 14, Amer. Math. Soc., 1962. LINKS N. J. A. Sloane, Table of n, a(n) for n = 1..10000 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.] David Applegate, The movie version Omar E. Pol, Illustration of initial terms (Fig. 1: one-step rook), (Fig. 2: one-step bishop), (Fig. 3: overlapping squares), (Fig. 4: overlapping X-toothpicks), 2009 Omar E. Pol, Illustration of initial terms of A139251, A160121, A147582 (Overlapping figures), 2009 D. Singmaster, On the cellular automaton of Ulam and Warburton, 2003 [Cached copy, included with permission] N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS N. J. A. Sloane, Exciting Number Sequences (video of talk), Mar 05 2021 FORMULA a(1) = 1; for n > 1, a(n) = 4*3^(wt(n-1)-1) where wt() = A000120(). - R. J. Mathar, Apr 30 2009 This formula is (essentially) given by Singmaster. - N. J. A. Sloane, Aug 06 2009 G.f.: x + 4*x*(Product_{k >= 0} (1 + 3*x^(2^k)) - 1)/3. - N. J. A. Sloane, Jun 10 2009 EXAMPLE From Omar E. Pol, Jun 14 2009: (Start) When written as a triangle: .1; .4; .4,12; .4,12,12,36; .4,12,12,36,12,36,36,108; .4,12,12,36,12,36,36,108,12,36,36,108,36,108,108,324; .4,12,12,36,12,36,36,108,12,36,36,108,36,108,108,324,12,36,36,108,36,108,... The rows converge to A161411. (End) MAPLE A000120 := proc(n) local w, m, i; w := 0; m := n; while m > 0 do i := m mod 2; w := w+i; m := (m-i)/2; od; w; end: wt := A000120; A147582 := n-> if n <= 1 then n else 4*3^(wt(n-1)-1); fi; [seq(A147582(n), n=0..1000)]; # N. J. A. Sloane, Apr 07 2010 MATHEMATICA s = Plus @@ Flatten@ # & /@ CellularAutomaton[{686, {2, {{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}}, {1, 1}}, {{{1}}, 0}, 200]; f[n_] = If[n == 0, 1, s[[n + 1]] - s[[n]]]; Array[f, 120, 0] (* Michael De Vlieger, Apr 09 2015, after Nadia Heninger and N. J. A. Sloane at A147562 *) CROSSREFS Cf. A147562, A147610 (the sequence divided by 4), A048881, A000120. Cf. A000079, A161411, A151779, A139250. Cf. A048883, A139251, A160121, A162349. [Omar E. Pol, Nov 02 2009] Cf. A323651. Sequence in context: A178182 A160721 A151836 * A162793 A269568 A169708 Adjacent sequences: A147579 A147580 A147581 * A147583 A147584 A147585 KEYWORD nonn AUTHOR N. J. A. Sloane, Apr 29 2009 EXTENSIONS Extended by R. J. Mathar, Apr 30 2009 STATUS approved

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