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 1-5 of 5 results.

A258730 T(n,k)=Number of length n+k 0..3 arrays with at most one downstep in every k consecutive neighbor pairs.

Original entry on oeis.org

16, 60, 64, 190, 225, 256, 512, 608, 840, 1024, 1212, 1408, 2028, 3136, 4096, 2592, 2936, 4184, 6552, 11704, 16384, 5115, 5664, 7834, 12549, 20955, 43681, 65536, 9460, 10280, 13720, 21860, 35540, 68120, 163020, 262144, 16588, 17754, 22866, 35704
Offset: 1

Views

Author

R. H. Hardin, Jun 08 2015

Keywords

Comments

Table starts
......16......60.....190.....512....1212....2592....5115....9460....16588
......64.....225.....608....1408....2936....5664...10280...17754....29416
.....256.....840....2028....4184....7834...13720...22866...36656....56925
....1024....3136....6552...12549...21860...35704...55660...83758...122584
....4096...11704...20955...35540...59188...92548..138196..199264...279560
...16384...43681...68120...98676..149960..228081..331584..465580...635992
...65536..163020..220854..281136..370510..526672..752180.1038256..1394568
..262144..608400..711432..819453..941024.1183616.1607656.2192682..2911776
.1048576.2270580.2300008.2358888.2487276.2727288.3343894.4392072..5783522
.4194304.8473921.7446144.6678576.6650600.6597449.7100132.8569478.10965340

Examples

			Some solutions for n=4 k=4
..1....1....0....0....3....0....1....3....2....0....2....3....0....3....2....0
..0....2....3....3....1....1....2....3....2....1....2....2....3....3....0....2
..2....0....3....1....1....1....3....3....0....1....3....3....0....0....2....2
..3....2....3....1....2....1....1....0....0....1....0....3....1....2....3....3
..3....3....3....1....2....1....1....0....1....1....0....3....3....3....3....0
..0....3....3....2....3....3....1....1....1....0....3....0....3....3....2....0
..0....3....1....3....0....0....2....3....2....0....3....2....1....0....2....2
..3....2....2....1....2....1....0....1....0....0....2....2....1....0....2....2
		

Crossrefs

Column 1 is A000302(n+1)
Column 2 is A072335(n+2)

Formula

Empirical for column k:
k=1: a(n) = 4*a(n-1)
k=2: a(n) = 4*a(n-1) -4*a(n-3) +a(n-4)
k=3: [order 8]
k=4: [order 12]
k=5: [order 16]
k=6: [order 19]
k=7: [order 22]
Empirical for row n:
n=1: [polynomial of degree 7]
n=2: [polynomial of degree 7]
n=3: [polynomial of degree 7] for n>1
n=4: [polynomial of degree 7] for n>2
n=5: [polynomial of degree 7] for n>3
n=6: [polynomial of degree 7] for n>4
n=7: [polynomial of degree 7] for n>5

A200785 T(n,k) is the number of arrays of n+2 elements from {0,1,...,k} with no two consecutive ascents.

Original entry on oeis.org

8, 26, 16, 60, 75, 32, 115, 225, 216, 64, 196, 530, 840, 622, 128, 308, 1071, 2425, 3136, 1791, 256, 456, 1946, 5796, 11100, 11704, 5157, 512, 645, 3270, 12152, 31395, 50775, 43681, 14849, 1024, 880, 5175, 23136, 75992, 169884, 232275, 163020, 42756, 2048
Offset: 1

Views

Author

R. H. Hardin Nov 22 2011

Keywords

Comments

All the conjectured formulas are true, and follow from the Burstein-Mansour paper. - N. J. A. Sloane, May 21 2013

Examples

			Table starts
....8.....26......60.......115.......196........308.........456.........645
...16.....75.....225.......530......1071.......1946........3270........5175
...32....216.....840......2425......5796......12152.......23136.......40905
...64....622....3136.....11100.....31395......75992......164004......324087
..128...1791...11704.....50775....169884.....474566.....1160616.....2562633
..256...5157...43681....232275....919413....2964416.....8216484....20273247
..512..14849..163020...1062500...4975322...18514405....58154912...160338680
.1024..42756..608400...4860250..26924106..115637431...411637168..1268210421
.2048.123111.2270580..22232375.145698840..722234149..2913595712.10030582998
.4096.354484.8473921.101698250.788446400.4510869636.20622837480.79335475611
Some arrays for n=4, k=3:
..0....1....0....0....1....0....3....3....0....1....3....0....2....2....2....2
..3....0....2....2....0....2....0....0....3....1....0....0....0....3....3....3
..2....3....2....2....2....2....3....3....1....0....1....0....2....1....3....3
..1....0....2....1....0....0....2....2....2....2....1....2....2....0....0....2
..0....3....0....0....1....2....1....2....0....0....3....2....0....3....1....3
..3....3....0....3....0....2....3....2....0....3....0....0....2....2....1....3
		

Crossrefs

Column 1 is A000079
Column 2 is A076264
Column 3 is A072335
Row 1 is A002413
Cf. A200781.

Formula

T(n-2,k) = \sum_{L=0}^n (-1)^L / L! * \sum_{M=0}^{min(L,[(n-L)/2])} binomial(n-L-M,M) * M! * (k+1)^(n-L-2*M) B_{L,M}(x_1,x_2,...), where B_{L,M}() are Bell polynomials, x_i = binomial(k+1,i+2) * i! * f(i), i=1,2,..., and f(i) has period of length 6: [0,1,1,0,-1,-1] (i.e., f(0)=0, f(1)=1, etc.). This formula implies that for a fixed n, T(n,k) is a polynomial in k, which is easy to compute. - Max Alekseyev, Dec 12 2011
Empirical formulas for columns:
k=1: a(n) = 2*a(n-1)
k=2: a(n) = 3*a(n-1) -a(n-3)
k=3: a(n) = 4*a(n-1) -4*a(n-3) +a(n-4)
k=4: a(n) = 5*a(n-1) -10*a(n-3) +5*a(n-4)
k=5: a(n) = 6*a(n-1) -20*a(n-3) +15*a(n-4) -a(n-6)
k=6: a(n) = 7*a(n-1) -35*a(n-3) +35*a(n-4) -7*a(n-6) +a(n-7)
k=7: a(n) = 8*a(n-1) -56*a(n-3) +70*a(n-4) -28*a(n-6) +8*a(n-7)
Empirical recurrence for general column k:
0 = sum{i=0..floor(k/3) (binomial(k+1,3*i+1)*T(n-(3*i+1),k))} - sum{i=0..floor((k+1)/3) (binomial(k+1,3*i)*T(n-3*i,k))}
Formulae for rows:
T(1,k) = (5/6)*k^3 + 3*k^2 + (19/6)*k + 1
T(2,k) = (17/24)*k^4 + (43/12)*k^3 + (151/24)*k^2 + (53/12)*k + 1
T(3,k) = (7/12)*k^5 + (47/12)*k^4 + (39/4)*k^3 + (133/12)*k^2 + (17/3)*k + 1
T(4,k) = (349/720)*k^6 + (321/80)*k^5 + (1883/144)*k^4 + (1013/48)*k^3 + (3139/180)*k^2 + (413/60)*k + 1
T(5,k) = (2017/5040)*k^7 + (1427/360)*k^6 + (5759/360)*k^5 + (607/18)*k^4 + (28459/720)*k^3 + (9113/360)*k^2 + (848/105)*k + 1
T(6,k) = (6679/20160)*k^8 + (4799/1260)*k^7 + (26449/1440)*k^6 + (2162/45)*k^5 + (212153/2880)*k^4 + (6019/90)*k^3 + (174571/5040)*k^2 + (3893/420)*k + 1
T(7,k) = (99377/362880)*k^9 + (48247/13440)*k^8 + (243673/12096)*k^7 + (60529/960)*k^6 + (2076437/17280)*k^5 + (274529/1920)*k^4 + (952027/9072)*k^3 + (152461/3360)*k^2 + (26399/2520)*k + 1

A072279 Dimension of n-th graded section of a certain Lie algebra.

Original entry on oeis.org

1, 4, 6, 16, 45, 144, 440, 1440, 4680, 15600, 52344, 177840, 608160, 2095920, 7262640, 25300032, 88517520, 310927680, 1095923400, 3874804560, 13737892896, 48829153920, 173949483240, 620963048160, 2220904271040, 7956987570576, 28553731537320, 102617166646800
Offset: 0

Views

Author

N. J. A. Sloane, Jul 15 2002

Keywords

Comments

Dimensions of Lie algebra associated to Yang-Lee algebra in the A. Connes and M. Dubois-Violette paper. - Roger L. Bagula, May 25 2007

Crossrefs

Inverse EULER transform of A072335 (with its initial 1 omitted).
Cf. A072337.

Programs

  • Maple
    with(numtheory): f:= proc(n) option remember; `if`(n<1, `if`(n=0,1,0), 4*(f(n-1)-f(n-3)) +f(n-4)) end: c:= proc(n) option remember; local j; n*f(n) -add(c(j)*f(n-j), j=1..n-1) end: a:= proc(n) option remember; local d; `if`(n=0,1, add(mobius(n/d)*c(d), d=divisors(n))/n) end: seq(a(n), n=0..27); # Alois P. Heinz, Sep 09 2008
  • Mathematica
    f[n_] := f[n] = If[n < 1, If[n == 0, 1, 0],  f[n-4] + 4*(f[n-1] - f[n-3])]; c[n_] := c[n] = n*f[n] - Sum[c[j]*f[n-j],  {j, 1, n-1}]; a[n_] := a[n] = If[n == 0, 1,  Sum[c[d]*MoebiusMu[n/d],  {d, Divisors[n]}]/n]; Table[a[n], {n, 0, 27}] (* Jean-François Alcover, Mar 14 2014, after Alois P. Heinz *)

Formula

Product_{n=1..inf} 1/(1-x^n)^a(n) = 1/((1-x^2)*(1-4*x+x^2)).
a(n) = (1/n) * Sum_{k|n} moebius(n/k) (t1^k + t2^k), where t1, t2 are the roots of x^2-4x+1.
a(n) ~ (2+sqrt(3))^n / n. - Vaclav Kotesovec, Sep 11 2014

Extensions

Edited by N. J. A. Sloane, May 16 2008 at the suggestion of R. J. Mathar

A225682 Triangle read by rows: T(n,k) (0 <= k <= n) = chi(k)*binomial(n,k), where chi(k) = 1,-1,0 according as k == 0,1,2 mod 3.

Original entry on oeis.org

1, 1, -1, 1, -2, 0, 1, -3, 0, 1, 1, -4, 0, 4, -1, 1, -5, 0, 10, -5, 0, 1, -6, 0, 20, -15, 0, 1, 1, -7, 0, 35, -35, 0, 7, -1, 1, -8, 0, 56, -70, 0, 28, -8, 0, 1, -9, 0, 84, -126, 0, 84, -36, 0, 1, 1, -10, 0, 120, -210, 0, 210, -120, 0, 10, -1, 1, -11, 0, 165, -330, 0, 462, -330, 0, 55, -11, 0, 1, -12, 0, 220, -495, 0, 924, -792, 0, 220, -66, 0, 1
Offset: 0

Views

Author

Keywords

Comments

Corresponding to row n of this triangle, define a generating function G_n(x) = 1/(Sum_{k=0..n} T(n,k)*x^k).
Then G_n(x) is the g.f. for the number of words of length n over an alphabet of size n which do not contain any strictly decreasing factor (consecutive subword) of length 3.
For example, G_2, G_3, G_4, G_5, G_6 are g.f.'s for A000079, A076264, A072335, A200781, A200782.

Examples

			Triangle begins:
[1],
[1, -1],
[1, -2, 0],
[1, -3, 0, 1],
[1, -4, 0, 4, -1],
[1, -5, 0, 10, -5, 0],
[1, -6, 0, 20, -15, 0, 1],
[1, -7, 0, 35, -35, 0, 7, -1],
[1, -8, 0, 56, -70, 0, 28, -8, 0],
...
		

Crossrefs

Programs

  • Maple
    f:=proc(n) local k,s;
    s:=k->if k mod 3 = 0 then 1 elif k mod 3 = 1 then -1 else 0; fi;
    [seq(s(k)*binomial(n,k),k=0..n)];
    end;
    [seq(f(n),n=0..12)];
  • Mathematica
    chi[k_] := Switch[Mod[k, 3], 0, 1, 1, -1, 2, 0]; t[n_, k_] := chi[k]*Binomial[n, k]; Table[t[n, k], {n, 0, 12}, {k, 0, n}] // Flatten (* Jean-François Alcover, Jan 14 2014 *)

A200781 G.f.: 1/(1-5*x+10*x^3-5*x^4).

Original entry on oeis.org

1, 5, 25, 115, 530, 2425, 11100, 50775, 232275, 1062500, 4860250, 22232375, 101698250, 465201250, 2127983750, 9734098125, 44526969375, 203681015625, 931704015625, 4261920875000, 19495429065625, 89178510250000, 407931862578125, 1866014626609375, 8535765175875000, 39045399804843750, 178606512071015625, 817004981729375000
Offset: 0

Views

Author

R. H. Hardin, Nov 22 2011

Keywords

Comments

Number of words of length n over an alphabet of size 5 which do not contain any strictly decreasing factor (consecutive subword) of length 3. For alphabets of size 2, 3, 4, 6 see A000079, A076264, A072335, A200782.
Equivalently, number of 0..4 arrays x(0..n-1) of n elements without any two consecutive increases.

Examples

			Some solutions for n=5:
..1....3....4....0....1....0....4....0....2....1....4....1....2....2....4....4
..3....4....4....2....1....0....3....3....1....4....1....1....4....4....3....3
..3....1....0....2....0....2....0....3....3....0....4....3....0....1....4....4
..2....0....2....4....4....0....3....2....0....0....3....2....0....2....1....3
..4....4....2....2....0....3....3....2....1....0....4....1....3....1....0....2
		

Crossrefs

The g.f. corresponds to row 5 of triangle A225682.
Column 4 of A200785.

Programs

  • PARI
    Vec(1/(1-5*x+10*x^3-5*x^4) + O(x^30)) \\ Jinyuan Wang, Mar 10 2020

Formula

a(n) = 5*a(n-1) - 10*a(n-3) + 5*a(n-4).

Extensions

Edited by N. J. A. Sloane, May 21 2013
Showing 1-5 of 5 results.