

A147582


First differences of A147562.


50



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
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OFFSET

1,2


REFERENCES

D. Singmaster, On the cellular automaton of Ulam and Warburton, M500 Magazine of the Open University, #195 (December 2003), pp. 27.
S. Ulam, On some mathematical problems connected with patterns of growth of figures, pp. 215224 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
David Applegate, The movie version
Omar E. Pol, Illustration of initial terms (Fig. 1: onestep rook), (Fig. 2: onestep bishop), (Fig. 3: overlapping squares), (Fig. 4: overlapping Xtoothpicks), 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


FORMULA

a(1)=1; for n > 1, a(n)=4*3^{wt(n1)1}.  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*(Prod_{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 := (mi)/2; od; w; end: wt := A000120; A147582 := n> if n <= 1 then n else 4*3^(wt(n1)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.
Cf. A000079, A161411, A151779, A139250.
Cf. A048883, A139251, A160121, A162349. [Omar E. Pol, Nov 02 2009]
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



