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 1-8 of 8 results.

A055203 Number of different relations between n intervals on a line.

Original entry on oeis.org

1, 1, 13, 409, 23917, 2244361, 308682013, 58514835289, 14623910308237, 4659168491711401, 1843200116875263613, 886470355671907534969, 509366445167037318008557, 344630301458257894126724041, 271188703889907190388528763613, 245570692377888837925941696215449
Offset: 0

Views

Author

Sylviane R. Schwer (schwer(AT)lipn.univ-paris13.fr), Jun 22 2000

Keywords

Comments

From Peter Bala, Jan 30 2018: (Start)
Number of alignments of n strings of length 2 (see Slowinski).
Conjectures: a(n) == 1 (mod 12); for fixed k, the sequence a(n) (mod k) eventually becomes periodic with exact period a divisor of phi(k), where phi(k) is Euler's totient function A000010. (End)

Examples

			In case n = 2 this is the Delannoy number a(2) = D(2,2) = 13.
a(2) = 13 because if you have two intervals [a1,a2] and [b1,b2], using a for a1 or a2 and b for b1 or b2 and writing c if an a is at the same place as a b, we get the following possibilities: aabb, acb, abab, cab, abc, baab, abba, cc, bac, cba, baba, bca, bbaa.
		

References

  • S. R. Schwer, Dépendances temporelles: les mots pour le dire, Journées Intelligence Artificielle, 1998.
  • S. R. Schwer, Enumerating and generating Allen's algebra, in preparation.

Crossrefs

Programs

  • Maple
    lambda := proc(p,n) option remember; if n = 1 then if p = 2 then RETURN(1) else RETURN(0) fi; else RETURN((p*(p-1)/2)*(lambda(p,n-1)+2*lambda(p-1,n-1)+lambda(p-2,n-1))) fi; end; A055203 := n->add(lambda(i,n),i=2..2*n);
    A055203 := proc(n) local k; add(A078739(n,k)*k!,k=0..2*n)/2^n end:
    seq(A055203(n),n=0..15); # Peter Luschny, Mar 25 2011
    # second Maple program:
    b:= proc(n) option remember; `if`(n=0, 1,
          add(b(n-j)*binomial(n, j), j=1..n))
        end:
    a:= n-> ceil(add(b(n+k)*binomial(n, k), k=0..n)/2^(n+1)):
    seq(a(n), n=0..20);  # Alois P. Heinz, Jul 10 2018
  • Mathematica
    a[n_] := Sum[((m-1)*m)^n / 2^(m+n+1), {m, 0, Infinity}]; Table[a[n], {n, 0, 15}] (* Jean-François Alcover, Oct 10 2011, after Vladeta Jovovic *)
    With[{r = 2}, Flatten[{1, Table[Sum[Sum[(-1)^i*Binomial[j, i]*Binomial[j - i, r]^k, {i, 0, j}], {j, 0, k*r}], {k, 1, 15}]}]] (* Vaclav Kotesovec, Mar 22 2016 *)

Formula

a(n) = Sum_{i=2..2n} lambda(i, n), with lambda(p, 1) = 1 if p = 2, otherwise 0; lambda(p, n) = (p*(p-1)/2)*(lambda(p, n-1) + 2*lambda(p-1, n-1) + lambda(p-2, n-1)).
lambda(p, n) = Sum_k[( - 1)^(p + k) * C(p, k) * ((k - 1)*k/2)^n]. So if T(m, 0), T(m, 1), ..., T(m, m) is any row of A035317 with m >= 2n - 1 then a(n) = Sum_j[(-1)^j * T(m, j) * ((m - j + 1)*(m - j)/2)^n]; e.g., a(2) = 13 = 1*6^2 - 3*3^2 + 4*1^2 - 2*0^2 = 1*10^2 - 4*6^2 + 7*3^2 - 6*1^2 + 3*0^2 = 1*15^2 - 5*10^2 + 11*6^2 - 13*3^2 + 9*1^2 - 3*0^2 etc. while a(3) = 409 = 1*15^3 - 5*10^3 + 11*6^3 - 13*3^3 + 9*1^3 - 3*0^3 etc. - Henry Bottomley, Jan 03 2001
Row sums of A122193. - Vladeta Jovovic, Aug 24 2006
a(n) = Sum_{k=0..n} k!*Stirling2(n,k)*A121251(k). - Vladeta Jovovic, Aug 25 2006
E.g.f.: Sum_{m>=0} exp(x*binomial(m,2))/2^(m+1). - Vladeta Jovovic, Sep 24 2006
a(n) = Sum_{m>=0} binomial(m,2)^n/2^(m+1). - Vladeta Jovovic, Aug 17 2006
a(n) = (1/2^n)*Sum_{k=0..n} (-1)^(n-k)*binomial(n,k)*A000670(n+k). - Vladeta Jovovic, Aug 17 2006
a(n) ~ n! * n^n * 2^(n-1) / (exp(n) * (log(2))^(2*n+1)). - Vaclav Kotesovec, Mar 15 2014
From Peter Bala, Jan 30 2018: (Start)
a(n) = Sum_{k = 2..2*n} Sum_{i = 0..k} (-1)^(k-i)*binomial(k,i)*(i*(i-1)/2)^n.
a(n) = (1/2^(n+1))*Sum_{k = 0..n} binomial(n,k)*A000670(n+k) for n >= 1. (End)

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), Oct 04 2000
More terms from N. J. A. Sloane, Jan 03 2001

A062109 Expansion of ((1-x)/(1-2*x))^4.

Original entry on oeis.org

1, 4, 14, 44, 129, 360, 968, 2528, 6448, 16128, 39680, 96256, 230656, 546816, 1284096, 2990080, 6909952, 15859712, 36175872, 82051072, 185139200, 415760384, 929562624, 2069889024, 4591714304, 10150215680, 22364028928, 49123688448, 107592286208, 235015241728, 512040632320
Offset: 0

Views

Author

Henry Bottomley, May 30 2001

Keywords

Comments

If X_1,X_2,...,X_n are 2-blocks of a (2n+4)-set X then, for n >= 1, a(n+1) is the number of (n+3)-subsets of X intersecting each X_i, (i=1,2,...,n). - Milan Janjic, Nov 23 2007
If the offset here is set to zero, the binomial transform of A006918. - R. J. Mathar, Jun 29 2009
a(n) is the number of weak compositions of n with exactly 3 parts equal to 0. - Milan Janjic, Jun 27 2010
Binomial transform of A002623. - Carl Najafi, Jan 22 2013
Except for an initial 1, this is the p-INVERT of (1,1,1,1,1,...) for p(S) = (1 - S)^4; see A291000. - Clark Kimberling, Aug 24 2017

Programs

  • Magma
    m:=30; R:=PowerSeriesRing(Integers(), m); Coefficients(R!(((1-x)/(1-2*x))^4)); // G. C. Greubel, Oct 16 2018
  • Maple
    seq(coeff(series(((1-x)/(1-2*x))^4, x,n+1),x,n),n=0..30); # Muniru A Asiru, Jul 01 2018
  • Mathematica
    CoefficientList[Series[(1 - x)^4/(1 - 2 x)^4, {x, 0, 26}], x] (* Michael De Vlieger, Jul 01 2018 *)
    LinearRecurrence[{8,-24,32,-16},{1,4,14,44,129},30] (* Harvey P. Dale, Sep 02 2022 *)
  • PARI
    a(n)=if(n<1,n==0,(n+5)*(n^2+13*n+18)*2^n/96)
    

Formula

a(n) = (n+5)*(n^2 + 13*n + 18)*2^(n-5)/3, with a(0)=1.
a(n) = A055809(n-5)*2^(n-4).
a(n) = 2*a(n-1) + A058396(n) - A058396(n-1).
a(n) = Sum_{kA058396(n).
a(n) = A062110(4, n).
G.f.: (1-x)^4/(1-2*x)^4.

A055807 Triangle T read by rows: T(i,j) = R(i-j,j), where R(i,0) = 1 for i >= 0, R(0,j) = 0 for j >= 1, and R(i,j) = Sum_{h=0..i-1, k=0..j} R(h,k) for i >= 1 and j >= 1.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 3, 1, 0, 1, 7, 4, 1, 0, 1, 15, 12, 5, 1, 0, 1, 31, 32, 18, 6, 1, 0, 1, 63, 80, 56, 25, 7, 1, 0, 1, 127, 192, 160, 88, 33, 8, 1, 0, 1, 255, 448, 432, 280, 129, 42, 9, 1, 0, 1, 511, 1024, 1120, 832, 450, 180, 52, 10, 1, 0, 1, 1023
Offset: 0

Views

Author

Clark Kimberling, May 28 2000

Keywords

Comments

Formatted as a triangular array, it is [1, 0, 1, 1, 0, 0, 0, 0, 0, ...] DELTA [0, 1, 0, -1, 1, 0, 0, 0, 0, ...] where DELTA is the operator defined in A084938. - Philippe Deléham, Nov 05 2006
The square array (R(n,k): n,k >= 0) referred to in the name of the sequence is actually A050143. - Petros Hadjicostas, Feb 13 2021

Examples

			Triangle T(n,k) (with rows n >= 0 and columns k = 0..n) begins:
  1;
  1,   0;
  1,   1,   0;
  1,   3,   1,   0;
  1,   7,   4,   1,   0;
  1,  15,  12,   5,   1,   0;
  1,  31,  32,  18,   6,   1,  0;
  1,  63,  80,  56,  25,   7,  1, 0;
  1, 127, 192, 160,  88,  33,  8, 1, 0;
  1, 255, 448, 432, 280, 129, 42, 9, 1, 0;
  ...
Florez et al. (2019) give the triangle in this form:
    1,    0,    0,   0,   0,   0,  0,  0, 0, ...
    3,    1,    0,   0,   0,   0,  0,  0, 0, ...
    7,    4,    1,   0,   0,   0,  0,  0, 0, ...
   15,   12,    5,   1,   0,   0,  0,  0, 0, ...
   31,   32,   18,   6,   1,   0,  0,  0, 0, ...
   63,   80,   56,  25,   7,   1,  0,  0, 0, ...
  127,  192,  160,  88,  33,   8,  1,  0, 0, ...
  255,  448,  432, 280, 129,  42,  9,  1, 0, ...
  511, 1024, 1120, 832, 450, 180, 52, 10, 1, ...
  ...
		

Crossrefs

Rows sums: A001519 (odd-indexed Fibonacci numbers).

Programs

  • GAP
    T:= function(i,j)
        if j=0 then return 1;
        elif i=0 then return 0;
        else return Sum([0..i-1], h-> Sum([0..j], m-> T(h,m) ));
        fi; end;
    Flat(List([0..12], n-> List([0..n], k-> T(n-k,k) ))); # G. C. Greubel, Jan 23 2020
  • Magma
    function T(i,j)
      if j eq 0 then return 1;
      elif i eq 0 then return 0;
      else return (&+[(&+[T(h,m): m in [0..j]]): h in [0..i-1]]);
      end if; return T; end function;
    [T(n-k,k): k in [0..n], n in [0..12]]; // G. C. Greubel, Jan 23 2020
    
  • Maple
    T:= proc(i, j) option remember;
          if j=0 then 1
        elif i=0 then 0
        else add(add(T(h,m), m=0..j), h=0..i-1)
          fi; end:
    seq(seq(T(n-k, k), k=0..n), n=0..12); # G. C. Greubel, Jan 23 2020
  • Mathematica
    T[i_, j_]:= T[i, j]= If[j==0, 1, If[i==0, 0, Sum[T[h, m], {h,0,i-1}, {m,0,j}]]]; Table[T[n-k, k], {n,0,12}, {k,0,n}]//Flatten (* G. C. Greubel, Jan 23 2020 *)
  • PARI
    T(i,j) = if(j==0, 1, if(i==0, 0, sum(h=0,i-1, sum(m=0,j, T(h,m) ))));
    for(n=0,12, for(k=0, n, print1(T(n-k,k), ", "))) \\ G. C. Greubel, Jan 23 2020
    
  • Sage
    @CachedFunction
    def T(i, j):
        if j==0: return 1
        elif i==0: return 0
        else: return sum(sum(T(h,m) for m in (0..j)) for h in (0..i-1))
    [[T(n-k, k) for k in (0..n)] for n in (0..12)] # G. C. Greubel, Jan 23 2020
    

Formula

T(2*n,n) = A050146(n).
G.f.: (1-2*x)*(1-x*y)/((1-x)*(1-x*y-2*x+x^2*y)). - R. J. Mathar, Aug 11 2015
From Petros Hadjicostas, Feb 13 2021: (Start)
T(n,k) = A050143(n-k, k) for 0 <= k <= n.
T(n,k) = (n-k)*hypergeom([-n + k + 1, k], [2], -1) = Sum_{s=1..n-k} binomial(n-k,s)*binomial(s+k-2,k-1) for 1 <= k <= n.
T(n,k) = 2*T(n-1,k) + T(n-1,k-1) - T(n-2,k-1) for 2 <= k <= n-1 with initial conditions T(n,0) = 1 for n >= 0, T(n,n) = 0 for n >= 1, and T(n,1) = 2^(n-1) - 1 for n >= 2. (End)

A055810 a(n) = T(n,n-5), array T as in A055807.

Original entry on oeis.org

1, 31, 80, 160, 280, 450, 681, 985, 1375, 1865, 2470, 3206, 4090, 5140, 6375, 7815, 9481, 11395, 13580, 16060, 18860, 22006, 25525, 29445, 33795, 38605, 43906, 49730, 56110, 63080, 70675, 78931, 87885, 97575
Offset: 5

Views

Author

Clark Kimberling, May 28 2000

Keywords

Crossrefs

Programs

  • GAP
    Concatenation([1], List([6..40], n-> (240 -54*n -49*n^2 +6*n^3 +n^4)/24 )); # G. C. Greubel, Jan 23 2020
  • Magma
    [1] cat [(240 -54*n -49*n^2 +6*n^3 +n^4)/24: n in [6..40]]; // G. C. Greubel, Jan 23 2020
    
  • Maple
    seq( `if`(n=5, 1, (240 -54*n -49*n^2 +6*n^3 +n^4)/24), n=5..40); # G. C. Greubel, Jan 23 2020
  • Mathematica
    Table[If[n==5, 1, (240 -54*n -49*n^2 +6*n^3 +n^4)/24], {n,5,40}] (* G. C. Greubel, Jan 23 2020 *)
  • PARI
    vector(40, n, my(m=n+4); if(m==5, 1, (240 -54*m -49*m^2 +6*m^3 +m^4)/24)) \\ G. C. Greubel, Jan 23 2020
    
  • Sage
    [1]+[(240 -54*n -49*n^2 +6*n^3 +n^4)/24 for n in (6..40)] # G. C. Greubel, Jan 23 2020
    

Formula

G.f.: x^5*(1 +26*x -65*x^2 +60*x^3 -25*x^4 +4*x^5)/(1-x)^5. - Colin Barker, Feb 22 2012
From G. C. Greubel, Jan 23 2020: (Start)
a(n) = (240 -54*n -49*n^2 +6*n^3 +n^4)/24 for n > 5, with a(5) = 1.
E.g.f.: (-1200 -720*x +100*x^3 +25*x^4 -4*x^5 + (1200 -480*x -120*x^2 +60*x^3 +5*x^4)*exp(x))/120. (End)

A055811 a(n) = T(n,n-6), array T as in A055807.

Original entry on oeis.org

1, 63, 192, 432, 832, 1452, 2364, 3653, 5418, 7773, 10848, 14790, 19764, 25954, 33564, 42819, 53966, 67275, 83040, 101580, 123240, 148392, 177436, 210801, 248946, 292361, 341568, 397122, 459612, 529662
Offset: 6

Views

Author

Clark Kimberling, May 28 2000

Keywords

Crossrefs

Programs

  • GAP
    Concatenation([1], List([7..30], n-> n*(1584 -310*n -85*n^2 +10*n^3 +n^4)/120 )); # G. C. Greubel, Jan 23 2020
  • Magma
    [1] cat [n*(1584 -310*n -85*n^2 +10*n^3 +n^4)/120: n in [7.30]]; // G. C. Greubel, Jan 23 2020
    
  • Maple
    seq( `if`(n=6, 1, n*(1584 -310*n -85*n^2 +10*n^3 +n^4)/120), n=6..30); # G. C. Greubel, Jan 23 2020
  • Mathematica
    Table[If[n==6,1, n*(1584 -310*n -85*n^2 +10*n^3 +n^4)/120], {n,6,30}] (* G. C. Greubel, Jan 23 2020 *)
  • PARI
    vector(25, n, my(m=n+5); if(m==6,1, m*(1584 -310*m -85*m^2 +10*m^3 +m^4)/120) ) \\ G. C. Greubel, Jan 23 2020
    
  • Sage
    [1]+[n*(1584 -310*n -85*n^2 +10*n^3 +n^4)/120 for n in (7..30)] # G. C. Greubel, Jan 23 2020
    

Formula

From G. C. Greubel, Jan 23 2020: (Start)
a(n) = n*(1584 - 310*n - 85*n^2 + 10*n^3 + n^4)/120 for n > 6, with a(6) = 1.
G.f.: x^6*(1 + 57*x - 171*x^2 + 205*x^3 - 125*x^4 + 39*x^5 - 5*x^6)/(1-x)^6.
E.g.f.: (-1)*x*(7200 +4320*x +720*x^2 -120*x^3 -54*x^4 +5*x^5 - (7200 -2880*x + 120*x^3 + 6*x^4)*exp(x))/720. (End)

A055815 a(n) = T(2*n+3,n), array T as in A055807.

Original entry on oeis.org

1, 15, 80, 432, 2352, 12896, 71136, 394400, 2196128, 12273648, 68811184, 386838480, 2179890000, 12309739968, 69641542848, 394643939904, 2239678552640, 12727572969680, 72415319422992, 412470467298032
Offset: 0

Views

Author

Clark Kimberling, May 28 2000

Keywords

Crossrefs

Apart from the offset the same as A050149. - R. J. Mathar, Oct 13 2008

Programs

  • Maple
    T:= proc(i, j) option remember;
          if j=0 then 1
        elif i=0 then 0
        else add(add(T(h,m), m=0..j), h=0..i-1)
      fi; end:
    seq(T(n+3, n), n=0..20); # G. C. Greubel, Jan 23 2020
  • Mathematica
    T[i_, j_]:= T[i, j]= If[j==0, 1, If[i==0, 0, Sum[T[h, m], {h,0,i-1}, {m,0,j}]]]; Table[T[n+3, n], {n,0,20}] (* G. C. Greubel, Jan 23 2020 *)
  • Sage
    @CachedFunction
    def T(i, j):
        if (j==0): return 1
        elif (i==0): return 0
        else: return sum(sum(T(h,m) for m in (0..j)) for h in (0..i-1))
    [T(n+3, n) for n in (0..20)] # G. C. Greubel, Jan 23 2020

Formula

a(n) = (n+3)*hypergeom([-n-2, n], [2], -1) = Sum_{s=1..n+3} binomial(n+3,s) * binomial(s+n-2,n-1) for n >= 1. - Petros Hadjicostas, Feb 13 2021

A055816 a(n) = T(2*n+4,n), array T as in A055807.

Original entry on oeis.org

1, 31, 192, 1120, 6400, 36288, 205184, 1159488, 6554880, 37088480, 210075712, 1191254688, 6762782208, 38434677120, 218663320320, 1245254943872, 7098135387648, 40495661150112, 231220652273600, 1321222104326880
Offset: 0

Views

Author

Clark Kimberling, May 28 2000

Keywords

Crossrefs

Programs

  • Maple
    T:= proc(i, j) option remember;
          if j=0 then 1
        elif i=0 then 0
        else add(add(T(h,m), m=0..j), h=0..i-1)
      fi; end:
    seq(T(n+4, n), n=0..20); # G. C. Greubel, Jan 23 2020
  • Mathematica
    T[i_, j_]:= T[i, j]= If[j==0, 1, If[i==0, 0, Sum[T[h, m], {h,0,i-1}, {m,0,j}]]]; Table[T[n+4, n], {n,0,20}] (* G. C. Greubel, Jan 23 2020 *)
  • Sage
    @CachedFunction
    def T(i, j):
        if (j==0): return 1
        elif (i==0): return 0
        else: return sum(sum(T(h,m) for m in (0..j)) for h in (0..i-1))
    [T(n+4, n) for n in (0..20)] # G. C. Greubel, Jan 23 2020

Formula

a(n) = (n+4)*hypergeom([-n -3, n], [2], -1) = Sum_{s=1..n+4} binomial(n+4,s)*binomial(s+n-2,n-1) for n >= 1. - Petros Hadjicostas, Feb 13 2021

A055817 a(n) = T(2n+5,n), array T as in A055807.

Original entry on oeis.org

1, 63, 448, 2816, 16896, 99200, 575872, 3322112, 19096064, 109541824, 627653440, 3594256896, 20577979392, 117814911744, 674630384384, 3864033226240, 22138650598400, 126885674577728, 727501822004416, 4172725286118656
Offset: 0

Views

Author

Clark Kimberling, May 28 2000

Keywords

Crossrefs

Programs

  • Maple
    T:= proc(i, j) option remember;
          if j=0 then 1
        elif i=0 then 0
        else add(add(T(h,m), m=0..j), h=0..i-1)
      fi; end:
    seq(T(n+5, n), n=0..20); # G. C. Greubel, Jan 23 2020
  • Mathematica
    T[i_, j_]:= T[i, j]= If[j==0, 1, If[i==0, 0, Sum[T[h, m], {h,0,i-1}, {m,0,j}]]]; Table[T[n+5, n], {n,0,20}] (* G. C. Greubel, Jan 23 2020 *)
  • Sage
    @CachedFunction
    def T(i, j):
        if (j==0): return 1
        elif (i==0): return 0
        else: return sum(sum(T(h,m) for m in (0..j)) for h in (0..i-1))
    [T(n+5, n) for n in (0..20)] # G. C. Greubel, Jan 23 2020

Formula

a(n) = (n+5)*hypergeom([-n-4, n], [2], -1) = Sum_{s=1..n+5} binomial(n+5,s) * binomial(s+n-2,n-1) for n >= 1. - Petros Hadjicostas, Feb 13 2021
Showing 1-8 of 8 results.