A124302 -id:A124302 - cp's OEIS frontend

A056477 Number of primitive (aperiodic) palindromic structures using a maximum of three different symbols.

1, 1, 0, 1, 1, 4, 3, 13, 12, 39, 36, 121, 116, 364, 351, 1088, 1080, 3280, 3237, 9841, 9800, 29510, 29403, 88573, 88440, 265716, 265356, 797121, 796796, 2391484, 2390352, 7174453, 7173360, 21523238, 21520080, 64570064, 64566684, 193710244, 193700403, 581130368, 581120880

Offset: 0

Marks R. Nester

nonn

Permuting the symbols will not change the structure.

M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]

Andrew Howroyd, Table of n, a(n) for n = 0..500

Cf. A007051, A124302, A056459, A284826.

a(n) = Sum_{d|n} mu(d)*A124302(ceiling(n/(2*d))) for n > 0.

a(n) = Sum_{k=1..3} A284826(n, k) for n > 0. - Andrew Howroyd, Oct 02 2019

a(0)=1 prepended and terms a(32) and beyond from Andrew Howroyd, Oct 02 2019

A107767 a(n) = (1 + 3^n - 23^(n/2))/4 if n is even, (1 + 3^n - 43^((n-1)/2))/4 if n odd.

Original entry on oeis.org

0, 1, 4, 16, 52, 169, 520, 1600, 4840, 14641, 44044, 132496, 397852, 1194649, 3585040, 10758400, 32278480, 96845281, 290545684, 871666576, 2615029252, 7845176329, 23535617560, 70607118400, 211821620920, 635465659921

Offset: 1

Emeric Deutsch, Jun 12 2005

a(n-1) is the number of chiral pairs of color patterns (set partitions) for a row of length n using up to 3 colors (subsets). For n=4, a(n-1)=4, the chiral pairs are AAAB-ABBB, AABA-ABAA, AABC-ABCC, and ABAC-ABCB. - Robert A. Russell, Oct 28 2018

Balaban, A. T., Brunvoll, J., Cyvin, B. N., & Cyvin, S. J. (1988). Enumeration of branched catacondensed benzenoid hydrocarbons and their numbers of Kekulé structures. Tetrahedron, 44(1), 221-228. See Eq. 5.

Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Gy. Tasi and F. Mizukami, Quantum algebraic-combinatoric study of the conformational properties of n-alkanes, J. Math. Chemistry, 25, 1999, 55-64 (see p. 60).
Index entries for linear recurrences with constant coefficients, signature (4,0,-12,9).

Cf. A167993 (first differences).
Column 3 of A320751, offset by 1.
Cf. A124302 (oriented), A001998 (unoriented), A182522 (achiral), varying offsets.

a:=[];; for n in [1..30] do if n mod 2 <> 0 then Add(a,(1+3^n-4*3^((n-1)/2))/4); else Add(a,(1+3^n-2*3^(n/2))/4); fi; od; a; # Muniru A Asiru, Oct 30 2018

I:=[0, 1, 4, 16]; [n le 4 select I[n] else 4*Self(n-1)-12*Self(n-3)+9*Self(n-4): n in [1..30]]; // Vincenzo Librandi, Jun 26 2012

a:=proc(n) if n mod 2 = 0 then (1+3^n-2*3^(n/2))/4 else (1+3^n-4*3^((n-1)/2))/4 fi end: seq(a(n),n=1..32);

CoefficientList[Series[-x/((x-1)*(3*x-1)*(3*x^2-1)),{x,0,40}],x] (* or *) LinearRecurrence[{4,0,-12,9},{0,1,4,16},50] (* Vincenzo Librandi, Jun 26 2012 *)
Ach[n_, k_] := Ach[n, k] = If[n<2, Boole[n==k && n>=0], k Ach[n-2,k] + Ach[n-2,k-1] + Ach[n-2,k-2]] (* A304972 *)
k=3; Table[Sum[StirlingS2[n,j]-Ach[n,j],{j,k}]/2,{n,2,40}] (* Robert A. Russell, Oct 28 2018 *)
CoefficientList[Series[(1/12 E^(-Sqrt[3] x) (-3 + 2 Sqrt[3] - (3 + 2 Sqrt[3]) E^(2 Sqrt[3] x) + 3 E^((3 + Sqrt[3]) x) + 3 E^(x + Sqrt[3] x)))/x, {x, 0, 20}], x]*Table[(k+1)!, {k, 0, 20}] (* Stefano Spezia, Oct 29 2018 *)

x='x+O('x^50); concat(0, Vec(x^2/((1-x)*(3*x-1)*(3*x^2-1)))) \\ Altug Alkan, Sep 23 2018

G.f.: -x^2 / ( (x-1)*(3*x-1)*(3*x^2-1) ). - R. J. Mathar, Dec 16 2010
a(n) = 4*a(n-1) - 12*a(n-3) + 9*a(n-4). - Vincenzo Librandi, Jun 26 2012
From Robert A. Russell, Oct 28 2018: (Start)
a(n-1) = Sum_{j=0..k} (S2(n,j) - Ach(n,j)) / 2, where k=3 is the maximum number of colors, S2 is the Stirling subset number A008277, and Ach(n,k) = [n>=0 & n<2 & n==k] + [n>1]*(k*Ach(n-2,k) + Ach(n-2,k-1) + Ach(n-2,k-2)).
a(n-1) = (A124302(n) - A182522(n))/2.
a(n-1) = A124302(n) - A001998(n-1).
a(n-1) = A001998(n-1) - A182522(n).
a(n-1) = A122746(n-2) + A320526(n). (End)
E.g.f.: (1/12)*exp(-sqrt(3)*x)*(-3 + 2*sqrt(3) - (3 + 2*sqrt(3))*exp(2*sqrt(3)*x) + 3*exp((3 + sqrt(3))*x) + 3*exp(x + sqrt(3)*x)). - Stefano Spezia, Oct 29 2018
From Bruno Berselli, Oct 31 2018: (Start)
a(n) = (1 + 3^n - 3^((n-1)/2)*(4 + (-2 + sqrt(3))*(1 + (-1)^n)))/4. Therefore:
a(2*k)   = (3^k - 1)^2/4;
a(2*k+1) = (3^k - 1)*(3^(k+1) - 1)/4. (End)

Entry revised by N. J. A. Sloane, Jul 29 2011

A147746 Riordan array (1, x(1-2x)/(1-3x+x^2)).

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 2, 2, 1, 0, 5, 5, 3, 1, 0, 13, 14, 9, 4, 1, 0, 34, 40, 28, 14, 5, 1, 0, 89, 114, 87, 48, 20, 6, 1, 0, 233, 323, 267, 161, 75, 27, 7, 1, 0, 610, 910, 809, 528, 270, 110, 35, 8, 1

Offset: 0

Paul Barry, Nov 11 2008

Triangle [0,1,1,1,0,0,0,....] DELTA [1,0,0,0,...] with Deléham DELTA as in A084938.
Note that 1/(1-x/(1-x/(1-x))) = (1-2x)/(1-3x+x^2). Row sums are A124302.
A147746*A007318 = A147747.

			Triangle begins
  1;
  0,   1;
  0,   1,   1;
  0,   2,   2,   1;
  0,   5,   5,   3,   1;
  0,  13,  14,   9,   4,   1;
  0,  34,  40,  28,  14,   5,   1;
  0,  89, 114,  87,  48,  20,   6,   1;
  ...

(* The function RiordanArray is defined in A256893. *)
RiordanArray[1&, # (1-2#)/(1-3#+#^2)&, 10] // Flatten (* Jean-François Alcover, Jul 19 2019 *)

Sum_{k=0..n} T(n,k)*2^k = A147748(n). - Philippe Deléham, Oct 30 2011
Sum_{k=0..n} T(n,k)*(-1)^(n-k) = A215936(n). - Philippe Deléham, Aug 30 2012
G.f.: (1 - 3*x + x^2)/(1 - 3*x + x^2 - x*y + 2*x^2*y). - R. J. Mathar, Aug 11 2015

A216238 Square array T, read by antidiagonals: T(n,k) = 0 if n-k>=1 or if k-n>=5, T(0,0) = T(0,1) = T(0,2) = T(0,3) = T(0,4) = 1, T(n,k) = T(n-1,k) + T(n,k-1).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 0, 0, 1, 3, 2, 0, 0, 0, 4, 5, 0, 0, 0, 0, 4, 9, 5, 0, 0, 0, 0, 0, 13, 14, 0, 0, 0, 0, 0, 0, 13, 27, 14, 0, 0, 0, 0, 0, 0, 0, 40, 41, 0, 0, 0, 0, 0, 0, 0, 0, 40, 81, 41, 0, 0, 0, 0, 0, 0, 0, 0, 0, 121, 122, 0, 0, 0, 0, 0, 0

Offset: 0

Philippe Deléham, Mar 14 2013

Hexagon arithmetic of E. Lucas.

			Square array begins:
1, 1, 1, 1,  1,  0,   0,   0,   0,    0,    0, ... row n=0
0, 1, 2, 3,  4,  4,   0,   0,   0,    0,    0, ... row n=1
0, 0, 2, 5,  9, 13,  13,   0,   0,    0,    0, ... row n=2
0, 0, 0, 5, 14, 27,  40,  40,   0,    0,    0, ... row n=3
0, 0, 0, 0, 14, 41,  81, 121, 121,    0,    0, ... row n=4
0, 0, 0, 0,  0, 41, 122, 243, 364,  364,    0, ... row n=5
0, 0, 0, 0,  0,  0, 122, 365, 729, 1093, 1093, ... row n=6
...

E. Lucas, Théorie des nombres, Albert Blanchard, Paris, 1958, Tome1, p.89

E. Lucas, Théorie des nombres, Tome 1, Jacques Gabay, Paris, 1991, p.89

Cf. A000244, A003462, A124302, A182522.

Similar sequences: A216201, A216210, A216216, A216218, A216219, A216220, A216226, A216228, A216229, A216230, A216232, A216235, A216236.

T(n,n) = A124302(n).
T(n,n+1) = A124302(n+1).
T(n,n+2) = 3^n = A000244(n).
T(n,n+3) = T(n,n+4) = A003462(n+1).
Sum_{k, 0<=k<=n} T(n-k,k) = A182522(n).

A262600 Number of Dyck paths of semilength n and height exactly 4.

Original entry on oeis.org

0, 0, 0, 0, 1, 7, 33, 132, 484, 1684, 5661, 18579, 59917, 190696, 600744, 1877256, 5828185, 17998783, 55342617, 169552428, 517884748, 1577812060, 4796682165, 14555626635, 44100374341, 133436026192, 403279293648, 1217616622992, 3673214880049, 11072960931319

Offset: 0

Ran Pan, Sep 25 2015

			a(4) = 1 because the only favorable path is UUUUDDDD.

Colin Barker, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (7,-16,13,-3).

Cf. A001519, A124302.

Column k=4 of A080936.

[((3^(n-1)+1)/2)-Fibonacci(2*n-1): n in [1.. 35]]; // Vincenzo Librandi, Sep 26 2015

CoefficientList[ Series[x^4/((x-1) (3 x-1) (x^2-3 x+1)), {x, 0, 30}], x]

a(n) = if( n<1, n==0, (3^(n-1) + 1) / 2) - fibonacci(2*n-1); vector(30, n, a(n-1)) \\ Altug Alkan, Sep 25 2015

concat(vector(4), Vec(x^4/((1-x)*(1-3*x)*(1-3*x+x^2)) + O(x^100))) \\ Colin Barker, Feb 08 2016

a(n) = A124302(n) - A001519(n).
G.f.: x^4/((x-1)*(3*x-1)*(x^2-3*x+1)).
a(n) = A080936(n,4).
From Colin Barker, Feb 08 2016: (Start)
a(n) = 7*a(n-1)-16*a(n-2)+13*a(n-3)-3*a(n-4) for n>4.
a(n) = 2^(-1-n)*(5*2^n*(3+3^n)+3*(-5+sqrt(5))*(3+sqrt(5))^n-3*(3-sqrt(5))^n*(5+sqrt(5)))/15 for n>0. (End)
E.g.f.: (2 + 3*exp(x) + exp(3*x))/6 - exp(3*x/2)*(5*cosh(sqrt(5)*x/2) - sqrt(5)*sinh(sqrt(5)*x/2))/5. - Stefano Spezia, May 21 2024

A092807 Expansion of (1-6x+4x^2)/((1-2x)(1-6*x)).

Original entry on oeis.org

1, 2, 8, 40, 224, 1312, 7808, 46720, 280064, 1679872, 10078208, 60467200, 362799104, 2176786432, 13060702208, 78364180480, 470185017344, 2821109972992, 16926659575808, 101559956930560, 609359740534784

Offset: 0

Paul Barry, Mar 06 2004

Second binomial transform of A054881 (closed walks at a vertex of an octahedron) With interpolated zeros, counts closed walks of length n at a vertex of the edge-vertex incidence graph of K_4 associated with the edges of K_4.

This also gives the number of noncrossing, nonnesting, 2-colored permutations on {1, 2, ..., n}. - Lily Yen, Apr 22 2013

G. C. Greubel, Table of n, a(n) for n = 0..1000
Lily Yen, Crossings and Nestings for Arc-Coloured Permutations, arXiv:1211.3472 [math.CO], 2012-2013 and Arc-coloured permutations, PSAC 2013, Paris, France, June 24-28, Proc. DMTCS (2013) 743-754.
Lily Yen, Crossings and Nestings for Arc-Coloured Permutations and Automation, Electronic Journal of Combinatorics, 22(1) (2015), #P1.14.
Index entries for linear recurrences with constant coefficients, signature (8,-12).

Cf. A054881, A074601, A092803, A124302.

[1] cat [6^(n-1) + 2^(n-1): n in [1..40]]; // G. C. Greubel, Jan 04 2023

CoefficientList[Series[(1-6x+4x^2)/((1-2x)(1-6x)),{x,0,40}],x] (* or *) LinearRecurrence[{8,-12},{1,2,8},41] (* Harvey P. Dale, Aug 23 2011 *)

[(6^n + 3*2^n + 2*0^n)/6 for n in range(41)] # G. C. Greubel, Jan 04 2023

G.f.: (1-6*x+4*x^2)/((1-2*x)*(1-6*x)).
a(n) = (6^n + 3*2^n + 2*0^n)/6.
a(n) = A074601(n-1), n>0. - R. J. Mathar, Sep 08 2008
a(0)=1, a(1)=2, a(2)=8, a(n) = 8*a(n-1)-12*a(n-2). - Harvey P. Dale, Aug 23 2011
a(n) = A124302(n)*2^n. - Philippe Deléham, Nov 01 2011
E.g.f.: (1/6)*( 1 + 3*exp(2*x) + exp(6*x) ). - G. C. Greubel, Jan 04 2023

A123183 a(1)=-1; a(2)=-1; a(3)=-2; a(n) = 4a(n-1) - 3a(n-2) for n >= 4.

Original entry on oeis.org

-1, -1, -2, -5, -14, -41, -122, -365, -1094, -3281, -9842, -29525, -88574, -265721, -797162, -2391485, -7174454, -21523361, -64570082, -193710245, -581130734, -1743392201, -5230176602, -15690529805, -47071589414, -141214768241, -423644304722, -1270932914165, -3812798742494

Offset: 1

Roger L. Bagula, Oct 02 2006

Essentially the same as A124302: a(n) = -A124302(n-1).

Index entries for linear recurrences with constant coefficients, signature (4,-3).

Cf. A124302.

a[1]:=-1: a[2]:=-1: a[3]:=-2: for n from 4 to 29 do a[n]:=4*a[n-1]-3*a[n-2] od: seq(a[n],n=1..29);

M = {{1, -1, 0}, {-1, 2, -1}, {0, -1, 1}} v[1] = {1, 0, 0} v[n_] := v[n] = M.v[n - 1] a1 = Table[ -v[n][[1]], {n, 1, 50}]

From Philippe Deléham, Dec 05 2008 [corrected by Sergei N. Gladkovskii, Dec 10 2012]: (Start)
a(n) = -A124302(n-1).
G.f.: -(1-3*x+x^2)/(1-4*x+3*x^2). (End)
G.f.: -1-x*G(0) where G(k) = 1 + 2*x/(1 - 2*x - x*(1-2*x)/(x + (1-2*x)*2/G(k+1))); (continued fraction). - Sergei N. Gladkovskii, Dec 10 2012

Edited by N. J. A. Sloane, Oct 08 2006

A135293 Differences between successive numbers whose sum of digits in base 3 is 2.

Original entry on oeis.org

2, 2, 2, 4, 2, 6, 10, 2, 6, 18, 28, 2, 6, 18, 54, 82, 2, 6, 18, 54, 162, 244, 2, 6, 18, 54, 162, 486, 730, 2, 6, 18, 54, 162, 486, 1458, 2188, 2, 6, 18, 54, 162, 486, 1458, 4374, 6562, 2, 6, 18, 54, 162, 486, 1458, 4374, 13122

Offset: 0

Adam Shelly (adam.shelly(AT)gmail.com), Dec 04 2007, Dec 05 2007

First differences of A052216 when the entries in that sequence are interpreted as base 3 numbers.

Can be regarded as a triangle, where T(0,0)=2, T(n+1,0) = T(n,0)+T(n,n), T(n+1,m) = T(n,m) for 0 < m <= n and T(n+1,n+1) = sum of T(n+1,0..n)

			triangle begins:
2
2 2
4 2 6
10 2 6 18
28 2 6 18 54
82 2 6 18 54 162
244 2 6 18 54 162 486.

G. C. Greubel, Table of n, a(n) for the first 50 rows

Cf. A052216.

T[0, 0] := 2; T[n_, 0] := 3^(n - 1) + 1; T[n_, m_] := 2*3^(m - 1); Table[T[n, m], {n, 0, 5}, {m, 0, n}] (* G. C. Greubel, Oct 09 2016 *)
Join[{2},Differences[Select[Range[50000],Total[IntegerDigits[#,3]]==2&]]] (* Harvey P. Dale, Jul 04 2019 *)

T(n,m) = 2*3^(m-1) = A025192(m) for m>0. T(n,0) = 2*A124302(n). - Franklin T. Adams-Watters, Sep 29 2011

Edited by Franklin T. Adams-Watters, Sep 29 2011

A198792 Triangle T(n,k), read by rows, given by (0,1,1,0,0,0,0,0,0,0,...) DELTA (1,0,0,1,0,0,0,0,0,0,0,...) where DELTA is the operator defined in A084938.

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 2, 2, 1, 0, 4, 6, 3, 1, 0, 8, 16, 12, 4, 1, 0, 16, 40, 40, 20, 5, 1, 0, 32, 96, 120, 80, 30, 6, 1, 0, 64, 224, 336, 280, 140, 42, 7, 1, 0, 128, 512, 896, 896, 560, 224, 56, 8, 1, 0, 256, 1152, 2304, 2688, 2016, 1008, 336, 72, 9, 1

Offset: 0

Philippe Deléham, Oct 30 2011

Row sums are A124302.

Variant of A119468.

			Triangle begins :
1
0, 1
0, 1, 1
0, 2, 2, 1
0, 4, 6, 3, 1
0, 8, 16, 12, 4, 1
0, 16, 40, 40, 20, 5, 1

Columns include A000007, A011782, A057711, A080929, A082138, A080951, A082139, A082140, A082141, A000012, A001477, A002378.

T(n,k) = A097805(n,k)*A011782(n-k).
Sum_{0<=k<=n} T(n,k)*2^k = A063376(n-1).
G.f.: (1-(y+2)*x+y*x^2)/((1-x*y)*(1-x*(y+2))).
T(n,k) = 2*T(n-1,k) + 2*T(n-1,k-1) - 2*T(n-2,k-1) - T(n-2,k-2) for n>2, T(0,0) = T(1,1) = T(2,2) = T(2,1) = 1, T(1,0) = T(2,0) = 0, T(n,k) = 0 if k<0 or if k>n. - Philippe Deléham, Nov 10 2013

A208736 Number of nonisomorphic graded posets with 0 and 1 and non-uniform Hasse graph of rank n, with exactly 2 elements of each rank level between 0 and 1.

Original entry on oeis.org

0, 0, 0, 1, 5, 22, 91, 361, 1392, 5265, 19653, 72694, 267179, 977593, 3565600, 12975457, 47142021, 171075606, 620303547, 2247803785, 8141857808, 29481675889, 106728951109, 386314552438, 1398132674955, 5059626441177, 18308871648576, 66249898660801

Offset: 0

David Nacin, Mar 01 2012

Uniform used in the sense of Retakh, Serconek and Wilson. We use Stanley's definition of graded poset: all maximal chains have the same length n (which also implies all maximal elements have maximal rank.)

R. Stanley, Enumerative combinatorics. Vol. 1, Cambridge University Press, Cambridge, 1997, pp. 96-100.

Vincenzo Librandi, Table of n, a(n) for n = 0..1000
V. Retakh, S. Serconek, and R. Wilson, Hilbert Series of Algebras Associated to Directed Graphs and Order Homology, arXiv:1010.6295 [math.RA], 2010-2011.
Wikipedia, Graded poset
Index entries for linear recurrences with constant coefficients, signature (8,-21,20,-5).

Cf. A208737, A206901, A206902, A206947-A206950, A001906, A025192, A081567, A124302, A124292, A088305, A086405, A012781.

Join[{0, 0}, LinearRecurrence[{8, -21, 20, -5}, {0, 1, 5, 22}, 40]]

def a(n, d={0:0,1:0,2:0,3:1,4:5,5:22}):
    if n in d:
        return d[n]
    d[n]=8*a(n-1) - 21*a(n-2) + 20*a(n-3) - 5*a(n-4)
    return d[n]

a(n) = 8*a(n-1) - 21*a(n-2) + 20*a(n-3) - 5*a(n-4), a(2) = 0, a(3) = 1, a(4) = 5, a(5) = 22.
G.f.: (x^3 - 3*x^4 + 3*x^5)/(1 - 8*x + 21*x^2 - 20*x^3 + 5*x^4); (x^3 * (1 - 3*x + 3*x^2))/((1 - 3*x + x^2)*(1 - 5*x + 5*x^2)) .
a(n) = A081567(n-2) - A001519(n-1).

cp's OEIS Frontend

A056477 Number of primitive (aperiodic) palindromic structures using a maximum of three different symbols.

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A107767 a(n) = (1 + 3^n - 2*3^(n/2))/4 if n is even, (1 + 3^n - 4*3^((n-1)/2))/4 if n odd.

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A147746 Riordan array (1, x(1-2x)/(1-3x+x^2)).

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A216238 Square array T, read by antidiagonals: T(n,k) = 0 if n-k>=1 or if k-n>=5, T(0,0) = T(0,1) = T(0,2) = T(0,3) = T(0,4) = 1, T(n,k) = T(n-1,k) + T(n,k-1).

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A262600 Number of Dyck paths of semilength n and height exactly 4.

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A092807 Expansion of (1-6*x+4*x^2)/((1-2*x)*(1-6*x)).

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A123183 a(1)=-1; a(2)=-1; a(3)=-2; a(n) = 4*a(n-1) - 3*a(n-2) for n >= 4.

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A107767 a(n) = (1 + 3^n - 23^(n/2))/4 if n is even, (1 + 3^n - 43^((n-1)/2))/4 if n odd.

A092807 Expansion of (1-6x+4x^2)/((1-2x)(1-6*x)).

A123183 a(1)=-1; a(2)=-1; a(3)=-2; a(n) = 4a(n-1) - 3a(n-2) for n >= 4.