A179133 -id:A179133 - cp's OEIS frontend

A153727 Period 3: repeat [1, 4, 2] ; Trajectory of 3x+1 sequence starting at 1.

1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2

Offset: 0

Philippe Deléham, Dec 30 2008

From Klaus Brockhaus, May 23 2010: (Start)
Continued fraction expansion of (7+sqrt(229))/18.
Decimal expansion of 142/999. (End)
a(A008585(n)) = 1; a(A016777(n)) = 4; a(A016789(n)) = 2. - Reinhard Zumkeller, Oct 08 2011

C. A. Pickover, The Math Book, 2009; Collatz Conjecture, pp 374-375.

Eric Weisstein's World of Mathematics, Collatz Problem
Wikipedia, Collatz conjecture
Index entries for sequences related to 3x+1 (or Collatz) problem
Index entries for linear recurrences with constant coefficients, signature (0,0,1).

Row 1 of A347270.
Cf. A178236 (decimal expansion of (7+sqrt(229))/18). Appears in A179133 (n>=1).
Cf. A006370, A080425, A130196, A131534.

a153727 n = a153727_list !! n
a153727_list = iterate a006370 1 -- Reinhard Zumkeller, Oct 08 2011

[2^(-n mod 3) : n in [0..50]]; // Wesley Ivan Hurt, Jun 20 2014

A153727:=n->2^(-n mod 3); seq(A153727(n), n=0..50); # Wesley Ivan Hurt, Jun 20 2014

a[n_] := {1, 4, 2}[[Mod[n, 3] + 1]]; Table[a[n], {n, 0, 104}] (* Jean-François Alcover, Jul 19 2013 *)
LinearRecurrence[{0, 0, 1},{1, 4, 2},105] (* Ray Chandler, Aug 25 2015 *)
PadRight[{},120,{1,4,2}] (* Harvey P. Dale, Jul 20 2025 *)

A153727(n)=[1,4,2][n%3+1] \\ M. F. Hasler, Feb 10 2011

[power_mod(2,-n,7)for n in range(0, 105)] # Zerinvary Lajos, Jun 07 2009

[power_mod(4, n, 7)for n in range(0, 105)] # Zerinvary Lajos, Nov 25 2009

a(3n)=1, a(3n+1)=4, a(3n+2)=2.
G.f.: (1+4*x+2*x^2)/(1-x^3).
a(n) = 4^n mod 7. - Zerinvary Lajos, Nov 25 2009
a(n) = A130196(n) * A131534(n). - Reinhard Zumkeller, Nov 12 2009
a(n) = 2^(-n mod 3) = 2^A080425(n). - Wesley Ivan Hurt, Jun 20 2014
a(n) = sqrt(4^(5*n) mod 21). - Gary Detlefs, Jul 07 2014
From Wesley Ivan Hurt, Jun 30 2016: (Start)
a(n) = a(n-3) for n>2.
a(n) = (7 - 4*cos(2*n*Pi/3) + 2*sqrt(3)*sin(2*n*Pi/3))/3. (End)

A178381 Number of paths of length n starting at initial node of the path graph P_9.

Original entry on oeis.org

1, 1, 2, 3, 6, 10, 20, 35, 70, 125, 250, 450, 900, 1625, 3250, 5875, 11750, 21250, 42500, 76875, 153750, 278125, 556250, 1006250, 2012500, 3640625, 7281250, 13171875, 26343750, 47656250, 95312500, 172421875, 344843750

Offset: 0

Johannes W. Meijer, May 27 2010, May 29 2010

Counts all paths of length n, n>=0, starting at initial node on the path graph P_9, see the Maple program.
The a(n) represent the number of possible chess games, ignoring the fifty-move and the triple repetition rules, after n moves by White in the following position: White Ka1, Nh1, pawns a2, b6, c2, d6, f2, g3 and g4; Black Ka8, Bc8, pawns a3, b7, c3, d7, f3 and g5.
The path graphs P_(2*p) have as limit(a(n+1)/a(n), n =infinity) = 2 resp. hypergeom([(p-1)/(2*p+1),(p+2)/(2*p+1)],[1/2],3/4) and the path graphs P_(2*p+1) have as limit(a(n+1)/a(n), n =infinity) = 1+cos(Pi/(p+1)), p>=1; see the crossrefs. - Johannes W. Meijer, Jul 01 2010

			G.f. = 1 + x + 2*x^2 + 3*x^3 + 6*x^4 + 10*x^5 + 20*x^6 + 35*x^7 + 70*x^8 + ...

G. C. Greubel, Table of n, a(n) for n = 0..1000
Johann Cigler, Some remarks and conjectures related to lattice paths in strips along the x-axis, arXiv:1501.04750 [math.CO], 2015-2016.
Nachum Dershowitz, Between Broadway and the Hudson, arXiv:2006.06516 [math.CO], 2020.
Eric Weisstein's World of Mathematics, Trigonometric Identities.
Index entries for linear recurrences with constant coefficients, signature (0,5,0,-5).

This is row 9 of A094718.
a(2*n) = A147748(n) and a(2*n+1) = A081567(n).
a(4*n+2) = A109106(n) and a(4*n+3) = A179135(n).
Cf. A000007 (P_1), A000012 (P_2), A016116 (P_3), A000045 (P_4), A038754 (P_5), A028495 (P_6), A030436 (P_7), A061551 (P_8), this sequence (P_9), A336675 (P_10), A336678 (P_11), and A001405 (P_infinity).
Cf. A216212 (P_9 starting in the middle).
Cf. A033191, A179131, A179132, A128052, A179133.

m:=50; R:=PowerSeriesRing(Integers(), m); Coefficients(R!((1+x-3*x^2-2*x^3+x^4)/(1-5*x^2+5*x^4))); // G. C. Greubel, Sep 18 2018

with(GraphTheory): P:=9: G:=PathGraph(P): A:= AdjacencyMatrix(G): nmax:=36; for n from 0 to nmax do B(n):=A^n; a(n):=add(B(n)[1,k],k=1..P); od: seq(a(n),n=0..nmax);
r := j -> (-1)^(j/10) - (-1)^(1-j/10):
a := k -> add((2 + r(j))*r(j)^k, j in [1, 3, 5, 7, 9])/10:
seq(simplify(a(n)), n=0..30); # Peter Luschny, Sep 18 2020

CoefficientList[Series[(1+x-3*x^2-2*x^3+x^4)/(1-5*x^2+5*x^4), {x,0,50}], x] (* G. C. Greubel, Sep 18 2018 *)

x='x+O('x^50); Vec((1+x-3*x^2-2*x^3+x^4)/(1-5*x^2+5*x^4)) \\ G. C. Greubel, Sep 18 2018

G.f.: (1+x-3*x^2-2*x^3+x^4)/(1-5*x^2+5*x^4).
a(n) = 5*a(n-2) - 5*a(n-4) for n>=5 with a(0)=1, a(1)=1, a(2)=2, a(3)=3 and a(4)=6.
G.f.: 1 / (1 - x / (1 - x / (1 + x / (1 + x / (1 - x / (1 - x / (1 + x / (1 + x)))))))). - Michael Somos, Feb 08 2015

A128052 a(n) = (F(2n-1) + F(2n+1))(5/6 - cos(2Pi*n/3)/3), where F(n) = Fibonacci(n).

Original entry on oeis.org

1, 3, 7, 9, 47, 123, 161, 843, 2207, 2889, 15127, 39603, 51841, 271443, 710647, 930249, 4870847, 12752043, 16692641, 87403803, 228826127, 299537289, 1568397607, 4106118243, 5374978561, 28143753123, 73681302247, 96450076809, 505019158607, 1322157322203

Offset: 0

Paul Barry, Feb 13 2007

The a(n+1) are the numerators of A178381(4*n+3)/A178381(4*n+2). For the denominators see A179133(n). - Johannes W. Meijer, Jul 01 2010

Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (0,0,18,0,0,-1).

Cf. A128053.

Cf. A179134. Trisection: A023039.

I:=[1,3,7,9,47,123]; [n le 6 select I[n] else 18*Self(n-3)-Self(n-6): n in [1..30]]; // Vincenzo Librandi, Jul 17 2019

with(combinat): nmax:=25; for n from 0 to nmax do a(n):= (fibonacci(2*n-1)+fibonacci(2*n+1))*(5/6-cos(2*Pi*n/3)/3) od: seq(a(n),n=0..nmax); # Johannes W. Meijer, Jul 01 2010

LinearRecurrence[{0, 0, 18, 0, 0, -1}, {1, 3, 7, 9, 47, 123}, 40] (* Vincenzo Librandi, Jul 17 2019 *)

Lim_{n->infinity} A128052(n+1)/A179133(n) = 1 + cos(Pi/5). - Johannes W. Meijer, Jul 01 2010
a(n) = Lucas(2*n)*(Fibonacci(n) mod 2 + 1)/2, Lucas(n)=A000032, Fibonacci(n)=A000045. - Gary Detlefs, Jan 19 2001
From Colin Barker, Jun 27 2013: (Start)
a(n) = 18*a(n-3) - a(n-6).
G.f: -(3*x^5 + 7*x^4 + 9*x^3 - 7*x^2 - 3*x - 1) / ((x^2 - 3*x + 1)*(x^4 + 3*x^3 + 8*x^2 + 3*x + 1)). (End)
With L(n) the Lucas number A000032, a(n) = L(2*n)/2 or L(2*n) according as n is, or is not, divisible by 3. - David Callan, Jul 17 2019

A179131 Numerators of A178381(4n+1)/A178381(4n).

Original entry on oeis.org

1, 5, 25, 65, 85, 445, 1165, 1525, 7985, 20905, 27365, 143285, 375125, 491045, 2571145, 6731345, 8811445, 46137325, 120789085, 158114965, 827900705, 2167472185, 2837257925, 14856075365, 38893710245, 50912527685, 266581455865

Offset: 0

Johannes W. Meijer, Jul 01 2010

For the denominators see A179132.

Index entries for linear recurrences with constant coefficients, signature (0,0,18,0,0,-1).

Cf. A128052, A179133, A179132.

with(GraphTheory): nmax:=116; P:=9: G:=PathGraph(P): A:= AdjacencyMatrix(G): for n from 0 to nmax do B(n):=A^n; A178381(n):=add(B(n)[1,k],k=1..P); od: for n from 0 to nmax-1 do a(n):= numer(A178381(4*n+1)/A178381(4*n)) od: seq(a(n),n=0..nmax/4-1);

a(n) = 5*A167808(2*n+1) for n>=1.
Limit(A179131(n)/A179132(n), n =infinity) = 1+cos(Pi/5) = A296182.
a(n) = 18*a(n-3)-a(n-6) for n>6. G.f.: -(4*x^6+5*x^5+5*x^4-47*x^3-25*x^2-5*x-1) / ((x^2-3*x+1)*(x^4+3*x^3+8*x^2+3*x+1)). - Colin Barker, Jun 27 2013

A179132 Denominators of A178381(4n+1)/A178381(4n).

Original entry on oeis.org

1, 3, 14, 36, 47, 246, 644, 843, 4414, 11556, 15127, 79206, 207364, 271443, 1421294, 3720996, 4870847, 25504086, 66770564, 87403803, 457652254, 1198149156, 1568397607, 8212236486, 21499914244, 28143753123, 147362604494

Offset: 0

Johannes W. Meijer, Jul 01 2010

For the numerators see A179131.

Index entries for linear recurrences with constant coefficients, signature (0,0,18,0,0,-1).

Cf. A128052 and A179133.

with(GraphTheory): nmax:=116; P:=9: G:=PathGraph(P): A:= AdjacencyMatrix(G): for n from 0 to nmax do B(n):=A^n; A178381(n):=add(B(n)[1,k],k=1..P); od: for n from 0 to nmax-1 do a(n):= denom(A178381(4*n+1)/A178381(4*n)) od: seq(a(n),n=0..nmax/4-1);

LinearRecurrence[{0,0,18,0,0,-1},{1,3,14,36,47,246,644},30] (* Harvey P. Dale, Jun 11 2022 *)

a(n) = A069705(n-1)*A128052(n) for n>=1.
Limit(A179131(n)/A179132(n), n =infinity) = 1+cos(Pi/5) = A296182.
a(n) = 18*a(n-3)-a(n-6) for n>6. G.f.: -(3*x^6+6*x^5+7*x^4-18*x^3-14*x^2-3*x-1) / ((x^2-3*x+1)*(x^4+3*x^3+8*x^2+3*x+1)). - Colin Barker, Jun 27 2013

A179134 a(n) = (F(2n-1) + F(2n+2)) * (5/6 - cos(2Pin/3)/3), where F(n) = Fibonacci(n).

Original entry on oeis.org

1, 4, 10, 13, 68, 178, 233, 1220, 3194, 4181, 21892, 57314, 75025, 392836, 1028458, 1346269, 7049156, 18454930, 24157817, 126491972, 331160282, 433494437, 2269806340, 5942430146, 7778742049, 40730022148, 106632582346

Offset: 0

Johannes W. Meijer, Jul 01 2010

Index entries for linear recurrences with constant coefficients, signature (0,0,18,0,0,-1).

Cf. A128052, A000045 (Fibonacci numbers).

Appears in A179133.

with(combinat): nmax:=28; for n from 0 to nmax do a(n):=(fibonacci(2*n-1)+fibonacci(2*n+2))*(5/6-cos(2*Pi*n/3)/3) od: seq(a(n),n=0..nmax);

a(n) = 18*a(n-3)-a(n-6). G.f.: -(2*x^5+4*x^4+5*x^3-10*x^2-4*x-1) / ((x^2-3*x+1)*(x^4+3*x^3+8*x^2+3*x+1)). - Colin Barker, Jun 27 2013

cp's OEIS Frontend

A153727 Period 3: repeat [1, 4, 2] ; Trajectory of 3x+1 sequence starting at 1.

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A178381 Number of paths of length n starting at initial node of the path graph P_9.

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A128052 a(n) = (F(2*n-1) + F(2*n+1))*(5/6 - cos(2*Pi*n/3)/3), where F(n) = Fibonacci(n).

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A179131 Numerators of A178381(4*n+1)/A178381(4*n).

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A179132 Denominators of A178381(4*n+1)/A178381(4*n).

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A179134 a(n) = (F(2*n-1) + F(2*n+2)) * (5/6 - cos(2*Pi*n/3)/3), where F(n) = Fibonacci(n).

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Formula

A128052 a(n) = (F(2n-1) + F(2n+1))(5/6 - cos(2Pi*n/3)/3), where F(n) = Fibonacci(n).

A179131 Numerators of A178381(4n+1)/A178381(4n).

A179132 Denominators of A178381(4n+1)/A178381(4n).

A179134 a(n) = (F(2n-1) + F(2n+2)) * (5/6 - cos(2Pin/3)/3), where F(n) = Fibonacci(n).