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A005666
Minimal number of moves for the cyclic variant of the Towers of Hanoi for 3 pegs and n disks, with the final peg two steps away.
(Formerly M1755)
1
0, 2, 7, 21, 59, 163, 447, 1223, 3343, 9135, 24959, 68191, 186303, 508991, 1390591, 3799167, 10379519, 28357375, 77473791, 211662335, 578272255, 1579869183, 4316282879, 11792304127, 32217174015, 88018956287, 240472260607, 656982433791, 1794909388799
OFFSET
0,2
COMMENTS
Original name was: Tower of Hanoi with 3 pegs and cyclic moves only (counterclockwise). - Jianing Song, Nov 01 2024
REFERENCES
R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics. Addison-Wesley, Reading, MA, 1990, p. 18.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
J.-P. Allouche, Note on the cyclic towers of Hanoi, Theoret. Comput. Sci., 123 (1994), 3-7.
M. D. Atkinson, The Cyclic Towers of Hanoi, Info. Proc. Letters, 13 (1981), 118-119.
Simon Plouffe, Approximations de séries génératrices et quelques conjectures, Dissertation, Université du Québec à Montréal, 1992; arXiv:0911.4975 [math.NT], 2009.
Simon Plouffe, 1031 Generating Functions, Appendix to Thesis, Montreal, 1992
D. G. Poole, The towers and triangles of Professor Claus (or, Pascal knows Hanoi), Math. Mag., 67 (1994), 323-344.
Amir Sapir, The Tower of Hanoi with Forbidden Moves, The Computer J. 47 (1) (2004) 20, case (ii), cyclic.
FORMULA
a(n) = (1/(4*s3))*((1+s3)^(n+2)-(1-s3)^(n+2))-1 where s3 = sqrt(3).
a(n) = A028859(n) - 1.
G.f.: x*(2+x) / ( (x-1)*(2*x^2+2*x-1) ). - Simon Plouffe in his 1992 dissertation
From Paul Zimmermann, Feb 07 2018: (Start)
a(n) = 2*a(n-1)+2*a(n-2)+3 (same recurrence as A005665).
a(n) = 2*a(n-1)+c(n-1)+2 where c(n) = 2*a(n-1)+1 stands for A005665. (End)
E.g.f.: exp(x)*(3*cosh(sqrt(3)*x) + 2*sqrt(3)*sinh(sqrt(3)*x) - 3)/3. - Stefano Spezia, Apr 11 2025
MATHEMATICA
CoefficientList[Series[z (2 + z)/(z - 1)/(2 z^2 + 2 z - 1), {z, 0, 22}], z] (* Michael De Vlieger, Sep 02 2015 *)
LinearRecurrence[{3, 0, -2}, {0, 2, 7}, 30] (* Harvey P. Dale, Jul 28 2025 *)
PROG
(Magma) [Floor((1/(4*Sqrt(3)))*((1+Sqrt(3))^(n+2)-(1-Sqrt(3))^(n+2))-1): n in [0..30]]; // Vincenzo Librandi, Sep 03 2015
CROSSREFS
Cf. A005665, A052945 (first differences).
Cf. A338024, A292764, A338089 (4 pegs).
Sequence in context: A018036 A007050 A320811 * A392848 A382988 A353094
KEYWORD
nonn,nice,easy
EXTENSIONS
Name clarified by Paul Zimmermann, Feb 09 2018
New name based on the name of A338024, A292764, and A338089 by Jianing Song, Nov 01 2024
STATUS
approved