cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-9 of 9 results.

A038261 First line of 5-wave sequence A038201, also bisection of A006358.

Original entry on oeis.org

1, 5, 55, 671, 8272, 102091, 1260143, 15554592, 191998646, 2369942427, 29253473175, 361091343583, 4457144547354, 55016930950608, 679103551405906, 8382540166524150, 103470199055689961, 1277188284212361415
Offset: 0

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Keywords

Programs

  • Maple
    a:= n-> (Matrix([[5, 1, 1, 2, 5]]). Matrix(5, (i,j)-> if i=j-1 then 1 elif j=1 then [15, -35, 28, -9, 1][i] else 0 fi)^n)[1,2]: seq(a(n), n=0..20); # Alois P. Heinz, Jul 16 2009

Formula

Conjecture: GF = -(x-1)*(x^3-6*x^2+9*x-1) / ( -1+15*x-35*x^2+28*x^3-9*x^4+x^5 ). - Wouter Meeussen, Mar 19 2005

A038339 Bottom line of 5-wave sequence A038201, also bisection of A006358.

Original entry on oeis.org

1, 15, 190, 2353, 29056, 358671, 4427294, 54648506, 674555937, 8326406594, 102777312308, 1268635610806, 15659451261015, 193293024178230, 2385919696236315, 29450689289430149, 363525688224433321
Offset: 0

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Comments

Denominator of g.f. is sum{k=0..5, (-1)^(k+1)*binomial(10-k,k)x^(5-k)}. This is det(J-x*I) where I is the 5x5 identity matrix and J is the matrix [1 1 0 0 0] [1 2 1 0 0] [0 1 2 1 0] [0 0 1 2 1] [0 0 0 1 2] - Paul Barry, May 11 2006

Programs

  • PARI
    k=5; M(k)=matrix(k,k,i,j,min(i,j)); v(k)=vector(k,i,1); a(n)=vecmax(v(k)*M(k)^n)

Formula

Let v(5)=(1, 1, 1, 1, 1), let M(5) be the 5 X 5 matrix m(i, j) =min(i, j); then a(n)= Max ( v(5)*M(5)^n) - Benoit Cloitre, Oct 03 2002
G.f.: 1/(1-15x+35x^2-28x^3+9x^4-x^5); - Paul Barry, May 11 2006

Extensions

More terms from Benoit Cloitre, Oct 03 2002

A038340 Second line of 5-wave sequence A038201.

Original entry on oeis.org

1, 4, 9, 50, 105, 616, 1287, 7601, 15873, 93819, 195910, 1158052, 2418195, 14294449, 29849041, 176444054, 368442700, 2177943781, 4547886208, 26883530748, 56137003923, 331837870408, 692929213991, 4096053203771, 8553197751125
Offset: 0

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Programs

  • Maple
    a:= n-> (Matrix([`if`(irem(n,2)=0, [9, 1, 0, -1, -4], [4, 0, -1, -3, -9])]). Matrix(5, (i,j)-> if i=j-1 then 1 elif j=1 then [15, -35, 28, -9, 1][i] else 0 fi)^iquo(n+1, 2))[1,2]: seq(a(n), n=0..24); # Alois P. Heinz, Jul 16 2009

Formula

G.f.: (x^7+x^6-6*x^5-5*x^4+10*x^3+6*x^2-4*x-1) / (x^10-9*x^8+28*x^6-35*x^4+15*x^2-1). - Alois P. Heinz, Jul 16 2009

A038341 Fourth line of 5-wave sequence A038201.

Original entry on oeis.org

1, 2, 14, 29, 175, 365, 2163, 4516, 26703, 55759, 329615, 688286, 4068623, 8495917, 50221212, 104869718, 619907431, 1294463368, 7651850657, 15978257251, 94450905714, 197228218022, 1165858298498, 2434493909304, 14390815650209
Offset: 0

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Crossrefs

Cf. A038201.

Programs

  • Maple
    a:= n-> (Matrix([[`if`(irem(n,2)=0, 1, 2), 0, 0, 0, -1]]). Matrix(5, (i,j)-> if i=j-1 then 1 elif j=1 then [15, -35, 28, -9, 1][i] else 0 fi) ^iquo(n, 2))[1,1]: seq(a(n), n=0..30); # Alois P. Heinz, Jul 16 2009

Formula

G.f.: (x^3+x^2-2*x-1) / (x^10-9*x^8+28*x^6-35*x^4+15*x^2-1). - Alois P. Heinz, Jul 16 2009

Extensions

More terms from Alois P. Heinz, Jul 16 2009

A006358 Number of distributive lattices; also number of paths with n turns when light is reflected from 5 glass plates.

Original entry on oeis.org

1, 5, 15, 55, 190, 671, 2353, 8272, 29056, 102091, 358671, 1260143, 4427294, 15554592, 54648506, 191998646, 674555937, 2369942427, 8326406594, 29253473175, 102777312308, 361091343583, 1268635610806, 4457144547354
Offset: 0

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Keywords

Comments

Let M denotes the 5 X 5 matrix = row by row (1,1,1,1,1)(1,1,1,1,0)(1,1,1,0,0)(1,1,0,0,0)(1,0,0,0,0) and A(n) the vector (x(n),y(n),z(n),t(n),u(n)) = M^n*A where A is the vector (1,1,1,1,1); then a(n)=y(n). - Benoit Cloitre, Apr 02 2002

References

  • J. Berman and P. Koehler, Cardinalities of finite distributive lattices, Mitteilungen aus dem Mathematischen Seminar Giessen, 121 (1976), 103-124.
  • S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (see p. 120).
  • J. Haubrich, Multinacci Rijen [Multinacci sequences], Euclides (Netherlands), Vol. 74, Issue 4, 1998, pp. 131-133.
  • D. E. Knuth, Art of Computer Programming, Vol. 3, Sect. 5.4.3, Column T1.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Cf. A038201 (5-wave sequence).

Programs

  • Maple
    A=seq(a.j,j=0..4):grammar1:=[Q4,{ seq(Q.i=Union(Epsilon,seq(Prod(a.j,Q.j),j=4-i..4)),i=0..4), seq(a.j=Z,j=0..4) }, unlabeled]: seq(count(grammar1,size=j),j=0..23); # Zerinvary Lajos, Mar 09 2007
    A006358:=-(z-1)*(z**3-3*z-1)/(-1+3*z+3*z**2-4*z**3-z**4+z**5); # conjectured by Simon Plouffe in his 1992 dissertation
  • Mathematica
    m = Table[ If[j <= 6-i, 1, 0], {i, 1, 5}, {j, 1, 5}] ; a[n_] := MatrixPower[m, n].Table[1, {5}]; Table[ a[n], {n, 0, 23}][[All, 1]] (* Jean-François Alcover, Dec 08 2011, after Benoit Cloitre *)
    LinearRecurrence[{3,3,-4,-1,1},{1,5,15,55,190},30] (* Harvey P. Dale, Jun 16 2016 *)
  • PARI
    k=5; M(k)=matrix(k,k,i,j,if(1-sign(i+j-k),0,1)); v(k)=vector(k,i,1); a(n)=vecmax(v(k)*M(k)^n)
    
  • PARI
    {a(n)=local(p=5);polcoeff(sum(k=0,p-1,(-1)^((k+1)\2)*binomial((p+k-1)\2,k)* (-x)^k)/sum(k=0,p,(-1)^((k+1)\2)*binomial((p+k)\2,k)*x^k+x*O(x^n)),n)}

Formula

a(n) = 3*a(n-1) + 3*a(n-2) - 4*a(n-3) - a(n-4) + a(n-5).
a(n) is asymptotic to z(5)*w(5)^n where w(5) = (1/2)/cos(5*Pi/11) and z(5) is the root 1 < x < 2 of P(5, X) = -1 + 55*X + 847*X^2 - 5324*X^3 - 14641*X^4 + 14641*X^5. - Benoit Cloitre, Oct 16 2002
G.f.: A(x) = (1 + 2*x - 3*x^2 - x^3 + x^4)/(1 - 3*x - 3*x^2 + 4*x^3 + x^4 - x^5). - Paul D. Hanna, Feb 06 2006

Extensions

Alternative description and formula from Jacques Haubrich (jhaubrich(AT)freeler.nl)
More terms from James Sellers, Dec 24 1999

A038196 3-wave sequence starting with 1, 1, 1.

Original entry on oeis.org

1, 1, 1, 2, 3, 5, 6, 11, 14, 25, 31, 56, 70, 126, 157, 283, 353, 636, 793, 1429, 1782, 3211, 4004, 7215, 8997, 16212, 20216, 36428, 45425, 81853, 102069, 183922, 229347, 413269, 515338, 928607, 1157954, 2086561, 2601899, 4688460, 5846414
Offset: 0

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Comments

The 3-wave sequence with initial values a, b, c is formed by the following construction:
a.......a+b+c............3a+5b+6c...
..b...b+c...a+2b+2c..2a+4b+5c...
....c..........a+2b+3c...

References

  • J. Kappraff, Beyond Measure, World Scientific, Inc. 2002, p. 497.

Crossrefs

a(2n) forms A006356, a(2n+1) ("the middle row") forms A006054. Cf. A038197, A038201, A187070.

Programs

  • PARI
    a(n)=if(n>-1,polcoeff((1+x-x^2)/(1-2*x^2-x^4+x^6)+x*O(x^n),n),if(n<-3,polcoeff((1-x-x^2)/(1-x^2-2*x^4+x^6)+O(x^(-3-n)),-4-n),0))

Formula

a(n) = a(n-1) + a(n-2) if n is odd,
a(n) = a(n-1) + a(n-4) if n is even.
Also: a(n) = 2*a(n-2) + a(n-4) - a(n-6).
G.f.: (1 + x - x^2)/(1 - 2*x^2 - x^4 + x^6).

Extensions

Edited by Floor van Lamoen, Feb 05 2002

A038197 4-wave sequence.

Original entry on oeis.org

1, 1, 1, 1, 2, 3, 4, 7, 9, 10, 19, 26, 30, 56, 75, 85, 160, 216, 246, 462, 622, 707, 1329, 1791, 2037, 3828, 5157, 5864, 11021, 14849, 16886, 31735, 42756, 48620, 91376, 123111, 139997, 263108, 354484, 403104, 757588, 1020696, 1160693, 2181389
Offset: 0

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Keywords

Comments

This sequence is related to the nonagon or 9-gon.

Examples

			The first few rows of the T(n,k) array are, n>=1, 1 <= k <=4:
  0,  0,   0,   1
  1,  1,   1,   1
  1,  2,   3,   4
  4,  7,   9,   10
  10, 19,  26,  30
  30, 56,  75,  85
  85, 160, 216, 246
		

Crossrefs

The a(3*n) lead to A006357; The T(n,k) lead to A076264 and A091024.
Cf. A120747 (m = 5: hendecagon or 11-gon)

Programs

  • Maple
    m:=4: nmax:=15: for k from 1 to m-1 do T(1,k):=0 od: T(1,m):=1: for n from 2 to nmax do for k from 1 to m do T(n,k):= add(T(n-1,k1), k1=m-k+1..m) od: od: for n from 1 to nmax/2 do seq(T(n,k), k=1..m) od; a(0):=1: Tx:=1: for n from 2 to nmax do for k from 2 to m do a(Tx):= T(n,k): Tx:=Tx+1: od: od: seq(a(n), n=0..Tx-1); # Johannes W. Meijer, Aug 03 2011
  • Mathematica
    LinearRecurrence[{1,-1,3,-3,3,0,0,0,-1,1,-1},{1,1,1,1,2,3,4,7,9,10,19},50] (* Harvey P. Dale, Oct 02 2015 *)

Formula

a(n) = a(n-1)+a(n-2) if n=3*m+1, a(n) = a(n-1)+a(n-4) if n=3*m+2, a(n) = a(n-1)+a(n-6) if n=3*m. Also: a(n) = 2*a(n-3)+3*a(n-6)-a(n-9)-a(n-12).
G.f.: -(-1-x-x^2+x^3-x^5+x^6)/(1-2*x^3-3*x^6+x^9+x^12)
a(n-1) = sequence(sequence(T(n,k), k=2..4), n>=2) with a(0)=1; T(n,k) = sum(T(n-1,k1), k1 = 5-k..4) with T(1,1) = T(1,2) = T(1,3) = 0 and T(1,4) = 1; n>=1 and 1 <= k <= 4. [Steinbach]

Extensions

Edited by Floor van Lamoen, Feb 05 2002
Edited and information added by Johannes W. Meijer, Aug 03 2011

A038342 G.f.: 1/(1 - 3 x - 3 x^2 + 4 x^3 + x^4 - x^5).

Original entry on oeis.org

1, 3, 12, 41, 146, 511, 1798, 6314, 22187, 77946, 273856, 962142, 3380337, 11876254, 41725295, 146595013, 515037713, 1809501081, 6357387289, 22335644540, 78472648463, 275700866485, 968630080476, 3403123989780
Offset: 0

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Comments

Middle line of 5-wave sequence A038201.
Let M denotes the 5 X 5 matrix = row by row (1,1,1,1,1)(1,1,1,1,0)(1,1,1,0,0)(1,1,0,0,0)(1,0,0,0,0) and A(n) the vector (x(n),y(n),z(n),t(n),u(n))=M^n*A where A is the vector (1,1,1,1,1) then a(n)=z(n). - Benoit Cloitre, Apr 02 2002
a(n) appears in the formula for 1/rho(11)^n, with rho(11) := 2*cos(Pi/11) (length ratio (smallest diagonal/side) in the regular 11-gom) when written in the power basis of the degree 5 number field Q(rho(11)): 1/rho(11)^n = a(n)*1 + A230080(n)*rho(11) - A230081(n)*rho(11)^2 - A069006(n-1)* rho(11)^3 + a(n-1)*rho(11)^4, n >= 0, with A069006(-1) = 0 = a(-1). See A230080 with the example for n=4. - Wolfdieter Lang, Nov 04 2013
From Wolfdieter Lang, Nov 20 2013: (Start)
The limit a(n+1)/a(n) for n -> infinity is omega(11) := S(4, x) = 1 - 3*x^2 + x^4 with x = rho(11). omega(11) = 1/(2*cos(Pi*5/11)), approx. 3.51333709. For the Chebyshev S-polynomial see A049310. For rho(11) see the preceding comment. The decimal expansion of omega(11) is given in A231186. omega(11) is an integer in Q(rho(11)) with power basis coefficients [1,0,-3,0,1]. It is known to be the length ratio (longest diagonal)/side in the regular 11-gon.
This limit follows from the a(n)-recurrence and the solutions of X^5 - 3*X^4 - 3*X^3 + 4*X^2 + X - 1 = 0, which are given by the inverse of the known solutions of the minimal polynomial C(11, x) of rho(11) (see A187360). The other four X solutions are 1/rho(11), with coefficients [3,3,-4,-1,1] in the power basis of Q(rho(11)), approx. 0.52110856, 1/(2*cos(Pi*3/11)) with coefficients [-1,-1,1,0,0], approx. 0.763521119, 1/(2*cos(Pi*7/11)) with coefficients [0,-3,3,1,-1], approx. -1.20361562, and 1/(2*cos(Pi*9/11)) with coefficients [0,1,3,0,-1], approx. -0.59435114. These solutions for X are therefore irrelevant for this sequence.
The same limit omega(11) is therefore obtained for the sequences A069006, A230080 and A230081. See the Nov 04 2013 comment.
(End)

References

  • Jay Kappraff, Beyond Measure, A Guided Tour Through Nature, Myth and Number, World Scientific, 2002.

Crossrefs

Cf. A006358, A069006, A230080, A230081: same recurrence formula.
Cf. A066170.

Programs

  • Mathematica
    b = {-1, 3, 3, -4, -1, 1}; p[x_] := Sum[x^(n - 1)*b[[7 - n]], {n, 1, 6}] q[x_] := ExpandAll[x^5*p[1/x]] Table[ SeriesCoefficient[ Series[x/q[x], {x, 0, 30}], n], {n, 0, 30}] (* Roger L. Bagula and Gary W. Adamson, Sep 19 2006 *)
    LinearRecurrence[{3,3,-4,-1,1},{1,3,12,41,146},30] (* Harvey P. Dale, Aug 27 2012 *)

Formula

a(n) = 3a(n-1)+3a(n-2)-4a(n-3)-a(n-4)+a(n-5). Also a(n) = b(4n+2) with b(n) as in 5-wave sequence A038201.
G.f.: 1/(1 - 3 x - 3 x^2 + 4 x^3 + x^4 - x^5) = -1/C(11, x), with C(11, x) the minimal polynomial of 2*cos(Pi/11) (see the name and A187360 for C). - Wolfdieter Lang, Nov 07 2013

Extensions

More terms from Benoit Cloitre, Apr 02 2002
Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, Jun 08 2007

A120747 Sequence relating to the 11-gon (or hendecagon).

Original entry on oeis.org

0, 1, 4, 14, 50, 175, 616, 2163, 7601, 26703, 93819, 329615, 1158052, 4068623, 14294449, 50221212, 176444054, 619907431, 2177943781, 7651850657, 26883530748, 94450905714, 331837870408, 1165858298498, 4096053203771, 14390815650209, 50559786403254
Offset: 1

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Author

Gary W. Adamson, Jul 01 2006

Keywords

Comments

The hendecagon is an 11-sided polygon. The preferred word in the OEIS is 11-gon.
The lengths of the diagonals of the regular 11-gon are r[k] = sin(k*Pi/11)/sin(Pi/11), 1 <= k <= 5, where r[1] = 1 is the length of the edge.
The value of limit(a(n)/a(n-1),n=infinity) equals the longest diagonal r[5].
The a(n) equal the matrix elements M^n[1,2], where M = Matrix([[1,1,1,1,1], [1,1,1,1,0], [1,1,1,0,0], [1,1,0,0,0], [1,0,0,0,0]]). The characteristic polynomial of M is (x^5 - 3x^4 - 3x^3 + 4x^2 + x - 1) with roots x1 = -r[4]/r[3], x2 = -r[2]/r[4], x3 = r[1]/r[2], x4 = r[3]/r[5] and x5 = r[5]/r[1].
Note that M^4*[1,0,0,0,0] = [55, 50, 41, 29, 15] which are all terms of the 5-wave sequence A038201. This is also the case for the terms of M^n*[1,0,0,0,0], n>=1.

Examples

			From _Johannes W. Meijer_, Aug 03 2011: (Start)
The lengths of the regular hendecagon edge and diagonals are:
  r[1] = 1.000000000, r[2] = 1.918985948, r[3] = 2.682507066,
  r[4] = 3.228707416, r[5] = 3.513337092.
The first few rows of the T(n,k) array are, n>=1, 1 <= k <=5:
    0,   0,   0,   0,   1, ...
    1,   1,   1,   1,   1, ...
    1,   2,   3,   4,   5, ...
    5,   9,  12,  14,  15, ...
   15,  29,  41,  50,  55, ...
   55, 105, 146, 175, 190, ...
  190, 365, 511, 616, 671, ... (End)
		

Crossrefs

From Johannes W. Meijer, Aug 03 2011: (Start)
Cf. A006358 (T(n+2,1) and T(n+1,5)), A069006 (T(n+1,2)), A038342 (T(n+1,3)), this sequence (T(n,4)) (m=5: hendecagon or 11-gon).
Cf. A000045 (m=2; pentagon or 5-gon); A006356, A006054 and A038196 (m=3: heptagon or 7-gon); A006357, A076264, A091024 and A038197 (m=4: enneagon or 9-gon); A006359, A069007, A069008, A069009, A070778 (m=6; tridecagon or 13-gon); A025030 (m=7: pentadecagon or 15-gon); A030112 (m=8: heptadecagon or 17-gon). (End)

Programs

  • Magma
    R:=PowerSeriesRing(Integers(), 40); [0] cat Coefficients(R!( x^2*(1+x-x^2)/(1-3*x-3*x^2+4*x^3+x^4-x^5) )); // G. C. Greubel, Nov 13 2022
    
  • Maple
    nmax:=27: m:=5: for k from 1 to m-1 do T(1,k):=0 od: T(1,m):=1: for n from 2 to nmax do for k from 1 to m do T(n,k):= add(T(n-1,k1), k1=m-k+1..m) od: od: for n from 1 to nmax/3 do seq(T(n,k), k=1..m) od; for n from 1 to nmax do a(n):=T(n,4) od: seq(a(n), n=1..nmax); # Johannes W. Meijer, Aug 03 2011
  • Mathematica
    LinearRecurrence[{3, 3, -4, -1, 1}, {0, 1, 4, 14, 50}, 41] (* G. C. Greubel, Nov 13 2022 *)
  • SageMath
    def A120747_list(prec):
        P. = PowerSeriesRing(ZZ, prec)
        return P( x*(1+x-x^2)/(1-3*x-3*x^2+4*x^3+x^4-x^5) ).list()
    A120747_list(40) # G. C. Greubel, Nov 13 2022

Formula

a(n) = 3*a(n-1) + 3*a(n-2) - 4*a(n-3) - a(n-4) + a(n-5).
G.f.: x^2*(1+x-x^2)/(1-3*x-3*x^2+4*x^3+x^4-x^5). - Maksym Voznyy (voznyy(AT)mail.ru), Aug 12 2009
From Johannes W. Meijer, Aug 03 2011: (Start)
a(n) = T(n,4) with T(n,k) = Sum_{k1 = 6-k..6} T(n-1, k1), T(1,1) = T(1,2) = T(1,3) = T(1,4) = 0 and T(1,5) = 1, n>=1 and 1 <= k <= 5. [Steinbach]
Sum_{k=1..5} T(n,k)*r[k] = r[5]^n, n>=1. [Steinbach]
r[k] = sin(k*Pi/11)/sin(Pi/11), 1 <= k <= 5. [Kappraff]
Sum_{k=1..5} T(n,k) = A006358(n-1).
Limit_{n -> 00} T(n,k)/T(n-1,k) = r[5], 1 <= k <= 5.
sequence(sequence( T(n,k), k=2..5), n>=1) = A038201(n-4).
G.f.: (x^2*(x - x1)*(x - x2))/((x - x3)*(x - x4)*(x - x5)*(x - x6)*(x - x7)) with x1 = phi, x2 = (1-phi), x3 = r[1] - r[3], x4 = r[3] - r[5], x5 = r[5] - r[4], x6 = r[4] - r[2], x7 = r[2], where phi = (1 + sqrt(5))/2 is the golden ratio A001622. (End)

Extensions

Edited and information added by Johannes W. Meijer, Aug 03 2011
Showing 1-9 of 9 results.