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A047230 Numbers that are congruent to {3, 4} mod 6. 1
3, 4, 9, 10, 15, 16, 21, 22, 27, 28, 33, 34, 39, 40, 45, 46, 51, 52, 57, 58, 63, 64, 69, 70, 75, 76, 81, 82, 87, 88, 93, 94, 99, 100, 105, 106, 111, 112, 117, 118, 123, 124, 129, 130, 135, 136, 141, 142, 147, 148 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

If a(n) = the n-th Towers of Hanoi move, the smallest disc (#1) is on peg B. (Cf. A047264, A047239). For TOH moves 1 and 2, disc #1 is on peg C. For moves 3 and 4, it's on peg B, and for moves 5 and 6, it's on peg A. The cycle continues CBACBACBA... for moves (7,8), (9,10), (11,12), etc. So disc #1 is on peg B for TOH moves (3, 4, 9, 10, 15, 16, ...). - Gary W. Adamson Jun 22 2012

LINKS

Table of n, a(n) for n=1..50.

Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

FORMULA

a(n) = 6*n - a(n-1) - 5 (with a(1)=3). - Vincenzo Librandi, Aug 05 2010

From R. J. Mathar, Oct 08 2011: (Start)

a(n) = 3*n-1-(-1)^n.

G.f.: ( x*(3+x+2*x^2) ) / ( (1+x)*(x-1)^2 ).

(End)

MATHEMATICA

LinearRecurrence[{1, 1, -1}, {3, 4, 9}, 50] (* Harvey P. Dale, Dec 04 2018 *)

CROSSREFS

Sequence in context: A129783 A301919 A093513 * A277138 A126269 A319618

Adjacent sequences:  A047227 A047228 A047229 * A047231 A047232 A047233

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified October 20 20:08 EDT 2019. Contains 328271 sequences. (Running on oeis4.)