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.

Previous Showing 11-18 of 18 results.

A057089 Scaled Chebyshev U-polynomials evaluated at i*sqrt(6)/2. Generalized Fibonacci sequence.

Original entry on oeis.org

1, 6, 42, 288, 1980, 13608, 93528, 642816, 4418064, 30365280, 208700064, 1434392064, 9858552768, 67757668992, 465697330560, 3200729997312, 21998563967232, 151195763787264, 1039165966526976, 7142170381885440
Offset: 0

Views

Author

Wolfdieter Lang, Aug 11 2000

Keywords

Comments

a(n) gives the length of the word obtained after n steps with the substitution rule 0->1^6, 1->(1^6)0, starting from 0. The number of 1's and 0's of this word is 6*a(n-1) and 6*a(n-2), resp.

Crossrefs

Programs

Formula

a(n) = 6*a(n-1) + 6*a(n-2); a(0)=1, a(1)=6.
a(n) = S(n, i*sqrt(6))*(-i*sqrt(6))^n with S(n, x) := U(n, x/2), Chebyshev's polynomials of the 2nd kind, A049310.
G.f.: 1/(1-6*x-6*x^2).
a(n) = Sum_{k=0..n} 5^k*A063967(n,k). - Philippe Deléham, Nov 03 2006

A057091 Scaled Chebyshev U-polynomials evaluated at i*sqrt(2). Generalized Fibonacci sequence.

Original entry on oeis.org

1, 8, 72, 640, 5696, 50688, 451072, 4014080, 35721216, 317882368, 2828828672, 25173688320, 224020135936, 1993550594048, 17740565839872, 157872931471360, 1404907978489856, 12502247279689728, 111257242065436672, 990075914761011200, 8810665254611582976
Offset: 0

Views

Author

Wolfdieter Lang, Aug 11 2000

Keywords

Comments

a(n) gives the length of the word obtained after n steps with the substitution rule 0->1^8, 1->(1^8)0, starting from 0. The number of 1's and 0's of this word is 8*a(n-1) and 8*a(n-2), resp.

Programs

  • Magma
    I:=[1,8]; [n le 2 select I[n] else 8*Self(n-1) + 8*Self(n-2): n in [1..30]]; // G. C. Greubel, Jan 24 2018
  • Mathematica
    LinearRecurrence[{8,8}, {1,8}, 50] (* G. C. Greubel, Jan 24 2018 *)
  • PARI
    Vec(1/(1-8*x-8*x^2) + O(x^30)) \\ Colin Barker, Jun 14 2015
    
  • Sage
    [lucas_number1(n,8,-8) for n in range(0, 20)] # Zerinvary Lajos, Apr 25 2009
    

Formula

a(n) = 8*(a(n-1) + a(n-2)), a(-1)=0, a(0)=1.
a(n) = S(n, i*2*sqrt(2))*(-i*2*sqrt(2))^n with S(n, x) := U(n, x/2), Chebyshev's polynomials of the 2nd kind, A049310.
G.f.: 1/(1 - 8*x - 8*x^2).
a(n) = Sum_{k=0..n} 7^k*A063967(n,k). - Philippe Deléham, Nov 03 2006
a(n) = 2^n*A090017(n+1). - R. J. Mathar, Mar 08 2021

A057092 Scaled Chebyshev U-polynomials evaluated at i*3/2. Generalized Fibonacci sequence.

Original entry on oeis.org

1, 9, 90, 891, 8829, 87480, 866781, 8588349, 85096170, 843160671, 8354311569, 82777250160, 820184055561, 8126651751489, 80521522263450, 797833566134451, 7905195795581109, 78327264255440040, 776092140459190341, 7689774642431673429, 76192801046017773930
Offset: 0

Views

Author

Wolfdieter Lang, Aug 11 2000

Keywords

Comments

a(n) gives the length of the word obtained after n steps with the substitution rule 0->1^9, 1->(1^9)0, starting from 0. The number of 1's and 0's of this word is 9*a(n-1) and 9*a(n-2), resp.
a(n) gives the number of n-digit integers which have no digit repeated 3 times in a row. Example: a(2)= 90 which is all the 2-digit integers. a(3) = 891 = all 900 3-digit integers except 111, 222, 333, ..., 999. - Toby Gottfried, Apr 01 2013
a(n) is the number of n-digit integers which do not have two consecutive zeros. - Ran Pan, Jan 26 2016

Programs

  • Magma
    I:=[1,9]; [n le 2 select I[n] else 9*Self(n-1) + 9*Self(n-2): n in [1..30]]; // G. C. Greubel, Jan 25 2018
  • Mathematica
    Join[{a=0,b=1},Table[c=9*b+9*a;a=b;b=c,{n,100}]] (* Vladimir Joseph Stephan Orlovsky, Jan 17 2011 *)
    LinearRecurrence[{9,9}, {1,9}, 50] (* G. C. Greubel, Jan 25 2018 *)
  • PARI
    Vec(1/(1-9*x-9*x^2) + O(x^30)) \\ Colin Barker, Jun 14 2015
    
  • Sage
    [lucas_number1(n,9,-9) for n in range(1, 20)] # Zerinvary Lajos, Apr 26 2009
    

Formula

a(n) = 9*(a(n-1) + a(n-2)), a(-1)=0, a(0)=1.
a(n) = S(n, i*3)*(-i*3)^n with S(n, x) := U(n, x/2), Chebyshev's polynomials of the 2nd kind, A049310.
G.f.: 1/(1-9*x-9*x^2).
a(n) = Sum_{k, 0<=k<=n}8^k*A063967(n,k). - Philippe Deléham, Nov 03 2006

A057090 Scaled Chebyshev U-polynomials evaluated at i*sqrt(7)/2. Generalized Fibonacci sequence.

Original entry on oeis.org

1, 7, 56, 441, 3479, 27440, 216433, 1707111, 13464808, 106203433, 837677687, 6607167840, 52113918689, 411047605703, 3242130670744, 25572247935129, 201700650241111, 1590910287233680, 12548276562323537, 98974307946900519, 780658091564568392
Offset: 0

Views

Author

Wolfdieter Lang, Aug 11 2000

Keywords

Comments

a(n) gives the length of the word obtained after n steps with the substitution rule 0->1^7, 1->(1^7)0, starting from 0. The number of 1's and 0's of this word is 7*a(n-1) and 7*a(n-2), resp.

Crossrefs

Cf. A000045.

Programs

  • Magma
    I:=[1,7]; [n le 2 select I[n] else 7*Self(n-1) + 7*Self(n-2): n in [1..30]]; // G. C. Greubel, Jan 24 2018
  • Maple
    a:= n-> (<<0|1>, <7|7>>^n. <<1, 7>>)[1, 1]:
    seq(a(n), n=0..30);
  • Mathematica
    Join[{a=0,b=1},Table[c=7*b+7*a;a=b;b=c,{n,100}]] (* Vladimir Joseph Stephan Orlovsky, Jan 17 2011 *)
    LinearRecurrence[{7,7},{1,7},30] (* Harvey P. Dale, Nov 30 2012 *)
  • PARI
    Vec(1/(1-7*x-7*x^2) + O(x^30)) \\ Colin Barker, Jun 14 2015
    
  • Sage
    [lucas_number1(n,7,-7) for n in range(1, 21)] # Zerinvary Lajos, Apr 24 2009
    

Formula

a(n) = 7*(a(n-1) + a(n-2)), a(0)=1, a(1)=7.
a(n) = S(n, i*sqrt(7))*(-i*sqrt(7))^n with S(n, x) := U(n, x/2), Chebyshev's polynomials of the 2nd kind, A049310.
G.f.: 1/(1 - 7*x - 7*x^2).
a(n) = Sum_{k=0..n} 6^k*A063967(n,k). - Philippe Deléham, Nov 03 2006

A057093 Scaled Chebyshev U-polynomials evaluated at i*sqrt(10)/2. Generalized Fibonacci sequence.

Original entry on oeis.org

1, 10, 110, 1200, 13100, 143000, 1561000, 17040000, 186010000, 2030500000, 22165100000, 241956000000, 2641211000000, 28831670000000, 314728810000000, 3435604800000000, 37503336100000000, 409389409000000000, 4468927451000000000, 48783168600000000000
Offset: 0

Views

Author

Wolfdieter Lang, Aug 11 2000

Keywords

Comments

This is the m=10 member of the m-family of sequences a(m,n)= S(n,i*sqrt(m))*(-i*sqrt(m))^n, with S(n,x) given in Formula and g.f.: 1/(1-m*x-m*x^2). The instances m=1..9 are A000045 (Fibonacci), A002605, A030195, A057087, A057088, A057089, A057090, A057091, A057092.
With the roots rp(m) := (m+sqrt(m*(m+4)))/2 and rm(m) := (m-sqrt(m*(m+4)))/2 the Binet form of these m-sequences is a(n,m)= (rp(m)^(n+1)-rm(m)^(n+1))/(rp(m)-rm(m)).
a(n) gives the length of the word obtained after n steps with the substitution rule 0->1^10, 1->(1^10)0, starting from 0. The number of 1's and 0's of this word is 10*a(n-1) and 10*a(n-2), resp.

Programs

Formula

a(n) = 10*(a(n-1) + a(n-2)), a(-1)=0, a(0)=1.
a(n) = S(n, i*sqrt(10))*(-i*sqrt(10))^n with S(n, x) := U(n, x/2), Chebyshev's polynomials of the 2nd kind, A049310.
G.f.: 1/(1 - 10*x - 10*x^2).
a(n) = Sum_{k=0..n} 9^k*A063967(n,k). - Philippe Deléham, Nov 03 2006

Extensions

Extended by T. D. Noe, May 23 2011

A137644 a(n) = Sum_{k=0..n} C(n+k,k)*C(n+k,n-k).

Original entry on oeis.org

1, 3, 16, 95, 591, 3780, 24620, 162423, 1081780, 7258053, 48982176, 332140328, 2261099491, 15444137880, 105789736896, 726426836103, 4998885106599, 34464824536500, 238017084356680, 1646234203000485, 11401464090042224, 79060352485691272, 548829398923188036
Offset: 0

Views

Author

Paul D. Hanna, Jan 31 2008

Keywords

Comments

Number of lattice paths from (0,0) to (n,n) using steps (1,0), (1,1), (0,1), (0,2). - Eric Werley, Jun 29 2011
Diagonal of rational function 1/(1 - (x + y + x*y + x^2)). - Gheorghe Coserea, Aug 31 2018

Examples

			The triangle of number of lattice paths from (0,0) to (n,k) using steps (1,0), (1,1), (0,1), (0,2) begins:
  1;
  1,  3;
  1,  5,  16;
  1,  7,  29,  95;
  1,  9,  46, 179,  591;
  1, 11,  67, 303, 1140,  3780;
  1, 13,  92, 475, 2010,  7405, 24620;
  1, 15, 121, 703, 3309, 13427, 48761, 162423;
  1, 17, 154, 995, 5161, 22892, 90241, 324317, 1081780;
This sequence is the diagonal. - _Joerg Arndt_, Jul 01 2011
		

Crossrefs

Cf. A063967.

Programs

  • Mathematica
    Table[ HypergeometricPFQ[{-n, 1 + n, 1 + n}, {1/2, 1}, -(1/4)], {n,0,20}] (* Olivier Gérard, Apr 23 2009 *)
    Table[Sum[Binomial[n+k,k]Binomial[n+k,n-k],{k,0,n}],{n,0,20}] (* Harvey P. Dale, Aug 03 2011 *)
  • PARI
    a(n)=sum(k=0,n,binomial(n+k,k)*binomial(n+k,n-k))
    
  • PARI
    /* same as in A092566 but use */
    steps=[[1,0], [1,1], [0,1], [0,2]];
    /* Joerg Arndt, Jun 30 2011 */

Formula

a(n) = 3F2( {-n, n+1, n+1}; {1/2, 1})( -(1/4) ). - Olivier Gérard, Apr 23 2009
G.f.: F'(x)/(1+F(x)), where F(x)=x*(1+F(x))/(1-F(x)-F(x)^2). - Vladimir Kruchinin, Mar 24 2012
a(n) = A063967(n,n). - Alois P. Heinz, Oct 11 2017
a(n) ~ sqrt(56 + (7*(15953 - 267*sqrt(105)))^(1/3) + (7*(15953 + 267*sqrt(105)))^(1/3)) * (((36 + (44766 - 1050*sqrt(105))^(1/3) + (6*(7461 + 175*sqrt(105)))^(1/3))/15)^n / sqrt(210*Pi*n)). - Vaclav Kotesovec, Feb 17 2024

A129267 Triangle with T(n,k) = T(n-1,k-1) + T(n-1,k) - T(n-2,k-1) - T(n-2,k) and T(0,0)=1 .

Original entry on oeis.org

1, 1, 1, 0, 1, 1, -1, -1, 1, 1, -1, -3, -2, 1, 1, 0, -2, -5, -3, 1, 1, 1, 2, -2, -7, -4, 1, 1, 1, 5, 7, -1, -9, -5, 1, 1, 0, 3, 12, 15, 1, -11, -6, 1, 1, -1, -3, 3, 21, 26, 4, -13, -7, 1, 1, -1, -7, -15, -3, 31, 40, 8, -15, -8, 1, 1
Offset: 0

Views

Author

Philippe Deléham, Jun 08 2007

Keywords

Comments

Triangle T(n,k), 0<=k<=n, read by rows given by [1,-1,1,0,0,0,0,0,0,...] DELTA [1,0,0,0,0,0,...] where DELTA is the operator defined in A084938 . Riordan array (1/(1-x+x^2),(x*(1-x))/(1-x+x^2)); inverse array is (1/(1+x),(x/(1+x))*c(x/(1+x))) where c(x)is g.f. of A000108 .
Row sums are ( with the addition of a first row {0}): 0, 1, 2, 2, 0, -4, -8, -8, 0, 16, 32,... (see A009545). - Roger L. Bagula, Nov 15 2009

Examples

			Triangle begins:
   1;
   1,  1;
   0,  1,   1;
  -1, -1,   1,  1;
  -1, -3,  -2,  1,  1;
   0, -2,  -5, -3,  1,   1;
   1,  2,  -2, -7, -4,   1,   1;
   1,  5,   7, -1, -9,  -5,   1,   1;
   0,  3,  12, 15,  1, -11,  -6,   1,  1;
  -1, -3,   3, 21, 26,   4, -13,  -7,  1, 1;
  -1, -7, -15, -3, 31,  40,   8, -15, -8, 1, 1;
		

Crossrefs

Programs

  • Maple
    T:= proc(n, k) option remember;
          if k<0 or  k>n  then 0
        elif n=0 and k=0 then 1
        else T(n-1,k-1) + T(n-1,k) - T(n-2,k-1) - T(n-2,k)
          fi; end:
    seq(seq(T(n, k), k=0..n), n=0..12); # G. C. Greubel, Mar 14 2020
  • Mathematica
    m = {{a, 1}, {-1, 1}}; v[0]:= {0, 1}; v[n_]:= v[n] = m.v[n-1]; Table[CoefficientList[v[n][[1]], a], {n, 0, 10}]//Flatten (* Roger L. Bagula, Nov 15 2009 *)
    T[n_, k_]:= T[n, k]= If[k<0 || k>n, 0, If[n==0 && k==0, 1, T[n-1, k-1] + T[n-1, k] - T[n-2, k-1] - T[n-2, k] ]]; Table[T[n, k], {n,0,12}, {k,0,n}]//Flatten (* G. C. Greubel, Mar 14 2020 *)
  • Sage
    @CachedFunction
    def T(n, k):
        if (k<0 or k>n): return 0
        elif (n==0 and k==0): return 1
        else: return T(n-1,k-1) + T(n-1,k) - T(n-2,k-1) - T(n-2,k)
    [[T(n, k) for k in (0..n)] for n in (0..12)] # G. C. Greubel, Mar 14 2020

Formula

Sum{k=0..n} T(n,k)*x^k = { (-1)^n*A057093(n), (-1)^n*A057092(n), (-1)^n*A057091(n), (-1)^n*A057090(n), (-1)^n*A057089(n), (-1)^n*A057088(n), (-1)^n*A057087(n), (-1)^n*A030195(n+1), (-1)^n*A002605(n), A039834(n+1), A000007(n), A010892(n), A099087(n), A057083(n), A001787(n+1), A030191(n), A030192(n), A030240(n), A057084(n), A057085(n), A057086(n) } for x=-11, -10, ..., 8, 9, respectively .
Sum{k=0..n} T(n,k)*A000045(k) = A100334(n).
Sum{k=0..floor(n/2)} T(n-k,k) = A050935(n+2).
T(n,k)= Sum{j>=0} A109466(n,j)*binomial(j,k).
T(n,k) = (-1)^(n-k)*A199324(n,k) = (-1)^k*A202551(n,k) = A202503(n,n-k). - Philippe Deléham, Mar 26 2013
G.f.: 1/(1-x*y+x^2*y-x+x^2). - R. J. Mathar, Aug 11 2015

Extensions

Riordan array definition corrected by Ralf Stephan, Jan 02 2014

A199324 Triangle T(n,k), read by rows, given by (-1,1,-1,0,0,0,0,0,0,0,...) DELTA (1,0,0,0,0,0,0,0,0,0,...) where DELTA is the operator defined in A084938.

Original entry on oeis.org

1, -1, 1, 0, -1, 1, 1, -1, -1, 1, -1, 3, -2, -1, 1, 0, -2, 5, -3, -1, 1, 1, -2, -2, 7, -4, -1, 1, -1, 5, -7, -1, 9, -5, -1, 1, 0, -3, 12, -15, 1, 11, -6, -1, 1, 1, -3, -3, 21, -26, 4, 13, -7, -1, 1, -1, 7, -15, 3, 31, -40, 8, 15, -8, -1, 1, 0, -4, 22, -42
Offset: 0

Views

Author

Philippe Deléham, Nov 12 2011

Keywords

Examples

			Triangle begins :
1
-1, 1
0, -1, 1
1, -1, -1, 1
-1, 3, -2, -1, 1
0, -2, 5, -3, -1, 1
1, -2, -2, 7, -4, -1, 1
-1, 5, -7, -1, 9, -5, -1, 1
		

Crossrefs

Cf. A026729, A063967, A129267, A176971 (diagonals sums).

Formula

T(n,k)=T(n-1,k-1)+T(n-2,k-1)-T(n-1,k)-T(n-2,k), T(0,0)=1.
G.f.: 1/(1-(y-1)*x-(y-1)*x^2).
Sum_{k, 0<=k<=n}T(n,k)*x^k = A000748(n), A108520(n), A049347(n), A000007(n), A000045(n+1), A002605(n+1), A030195(n+1), A057087(n), A057088(n), A057089(n), A057090(n), A057091(n), A057092(n), A057093(n) for x = -2,-1,0,1,2,3,4,5,6,7,8,9,10,11 respectively.
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