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.

A077421 Chebyshev sequence U(n,11)=S(n,22) with Diophantine property.

Original entry on oeis.org

1, 22, 483, 10604, 232805, 5111106, 112211527, 2463542488, 54085723209, 1187422368110, 26069206375211, 572335117886532, 12565303387128493, 275864339398940314, 6056450163389558415, 132966039255171344816
Offset: 0

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Author

Wolfdieter Lang, Nov 29 2002

Keywords

Comments

b(n)^2 - 30*(2*a(n))^2 = 1 with the companion sequence b(n)=A077422(n+1).
For positive n, a(n) equals the permanent of the n X n tridiagonal matrix with 22's along the main diagonal, and i's along the subdiagonal and the superdiagonal (i is the imaginary unit). - John M. Campbell, Jul 08 2011
For n>=2, a(n) equals the number of 01-avoiding words of length n-1 on alphabet {0,1,...,21}. - Milan Janjic, Jan 25 2015

Crossrefs

Chebyshev sequence U(n, m): A000027 (m=1), A001353 (m=2), A001109 (m=3), A001090 (m=4), A004189 (m=5), A004191 (m=6), A007655 (m=7), A077412 (m=8), A049660 (m=9), A075843 (m=10), this sequence (m=11), A077423 (m=12), A097309 (m=13), A097311 (m=14), A097313 (m=15), A029548 (m=16), A029547 (m=17), A144128 (m=18), A078987 (m=19), A097316 (m=33).
Cf. A323182.

Programs

  • GAP
    m:=11;; a:=[1,2*m];; for n in [3..20] do a[n]:=2*m*a[n-1]-a[n-2]; od; a; # G. C. Greubel, Dec 23 2019
  • Magma
    I:=[1, 22]; [n le 2 select I[n] else 22*Self(n-1)-Self(n-2): n in [1..20]]; // Vincenzo Librandi, Dec 24 2012
    
  • Maple
    seq( simplify(ChebyshevU(n, 11)), n=0..20); # G. C. Greubel, Dec 23 2019
  • Mathematica
    Table[GegenbauerC[n, 1, 11], {n,0,20}] (* Vladimir Joseph Stephan Orlovsky, Sep 11 2008 *)
    CoefficientList[Series[1/(1-22x+x^2), {x,0,20}], x] (* Vincenzo Librandi, Dec 24 2012 *)
    ChebyshevU[Range[21] -1, 11] (* G. C. Greubel, Dec 23 2019 *)
  • PARI
    vector( 21, n, polchebyshev(n-1, 2, 11) ) \\ G. C. Greubel, Dec 23 2019
    
  • Sage
    [lucas_number1(n,22,1) for n in range(1,20)] # Zerinvary Lajos, Jun 25 2008
    
  • Sage
    [chebyshev_U(n,11) for n in (0..20)] # G. C. Greubel, Dec 23 2019
    

Formula

a(n) = 22*a(n-1) - a(n-1), a(-1)=0, a(0)=1.
a(n) = S(n, 22) with S(n, x) := U(n, x/2) Chebyshev's polynomials of the 2nd kind. See A049310.
a(n) = (ap^(n+1) - am^(n+1))/(ap - am) with ap := 11+2*sqrt(30) and am := 11-2*sqrt(30).
a(n) = Sum_{k=0..floor(n/2)} (-1)^k*binomial(n-k, k)*22^(n-2*k).
a(n) = sqrt((A077422(n+1)^2-1)/30)/2.
G.f.: 1/(1-22*x+x^2). - Philippe Deléham, Nov 18 2008
a(n) = Sum_{k, 0<=k<=n} A101950(n,k)*21^k. - Philippe Deléham, Feb 10 2012
Product {n >= 0} (1 + 1/a(n)) = 1/5*(5 + sqrt(30)). - Peter Bala, Dec 23 2012
Product {n >= 1} (1 - 1/a(n)) = 1/11*(5 + sqrt(30)). - Peter Bala, Dec 23 2012

A008310 Triangle of coefficients of Chebyshev polynomials T_n(x).

Original entry on oeis.org

1, 1, -1, 2, -3, 4, 1, -8, 8, 5, -20, 16, -1, 18, -48, 32, -7, 56, -112, 64, 1, -32, 160, -256, 128, 9, -120, 432, -576, 256, -1, 50, -400, 1120, -1280, 512, -11, 220, -1232, 2816, -2816, 1024, 1, -72, 840, -3584, 6912, -6144, 2048, 13, -364, 2912, -9984, 16640, -13312, 4096
Offset: 0

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Author

Keywords

Comments

The row length sequence of this irregular array is A008619(n), n >= 0. Even or odd powers appear in increasing order starting with 1 or x for even or odd row numbers n, respectively. This is the standard triangle A053120 with 0 deleted. - Wolfdieter Lang, Aug 02 2014
Let T* denote the triangle obtained by replacing each number in this triangle by its absolute value. Then T* gives the coefficients for cos(nx) as a polynomial in cos x. - Clark Kimberling, Aug 04 2024

Examples

			Rows are: (1), (1), (-1,2), (-3,4), (1,-8,8), (5,-20,16) etc., since if c = cos(x): cos(0x) = 1, cos(1x) = 1c; cos(2x) = -1+2c^2; cos(3x) = -3c+4c^3, cos(4x) = 1-8c^2+8c^4, cos(5x) = 5c-20c^3+16c^5, etc.
From _Wolfdieter Lang_, Aug 02 2014: (Start)
This irregular triangle a(n,k) begins:
  n\k   0    1     2      3      4      5      6      7 ...
  0:    1
  1:    1
  2:   -1    2
  3:   -3    4
  4:    1   -8     8
  5:    5  -20    16
  6:   -1   18   -48     32
  7:   -7   56  -112     64
  8:    1  -32   160   -256    128
  9:    9 -120   432   -576    256
 10:   -1   50  -400   1120  -1280    512
 11:  -11  220 -1232   2816  -2816   1024
 12:    1  -72   840  -3584   6912  -6144   2048
 13:   13 -364  2912  -9984  16640 -13312   4096
 14:   -1   98 -1568   9408 -26880  39424 -28672   8192
 15:  -15  560 -6048  28800 -70400  92160 -61440  16384
  ...
T(4,x) = 1 - 8*x^2 + 8*x^4, T(5,x) = 5*x - 20*x^3 +16*x^5.
(End)
		

References

  • M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 795.
  • E. A. Guilleman, Synthesis of Passive Networks, Wiley, 1957, p. 593.
  • Yaroslav Zolotaryuk, J. Chris Eilbeck, "Analytical approach to the Davydov-Scott theory with on-site potential", Physical Review B 63, p543402, Jan. 2001. The authors write, "Since the algebra of these is 'hyperbolic', contrary to the usual Chebyshev polynomials defined on the interval 0 <= x <= 1, we call the set of functions (21) the hyperbolic Chebyshev polynomials." (This refers to the triangle T* described in Comments.)

Crossrefs

A039991 is a row reversed version, but has zeros which enable the triangle to be seen. Columns/diagonals are A011782, A001792, A001793, A001794, A006974, A006975, A006976 etc.
Reflection of A028297. Cf. A008312, A053112.
Row sums are one. Polynomial evaluations include A001075 (x=2), A001541 (x=3), A001091, A001079, A023038, A011943, A001081, A023039, A001085, A077422, A077424, A097308, A097310, A068203.
Cf. A053120.

Programs

  • Maple
    A008310 := proc(n,m) local x ; coeftayl(simplify(ChebyshevT(n,x),'ChebyshevT'),x=0,m) ; end: i := 0 : for n from 0 to 100 do for m from n mod 2 to n by 2 do printf("%d %d ",i,A008310(n,m)) ; i := i+1 ; od ; od ; # R. J. Mathar, Apr 20 2007
    # second Maple program:
    b:= proc(n) b(n):= `if`(n<2, 1, expand(2*b(n-1)-x*b(n-2))) end:
    T:= n-> (p-> (d-> seq(coeff(p, x, d-i), i=0..d))(degree(p)))(b(n)):
    seq(T(n), n=0..15);  # Alois P. Heinz, Sep 04 2019
  • Mathematica
    Flatten[{1, Table[CoefficientList[ChebyshevT[n, x], x], {n, 1, 13}]}]//DeleteCases[#, 0, Infinity]& (* or *) Flatten[{1, Table[Table[((-1)^k*2^(n-2 k-1)*n*Binomial[n-k, k])/(n-k), {k, Floor[n/2], 0, -1}], {n, 1, 13}]}] (* Eugeniy Sokol, Sep 04 2019 *)

Formula

a(n,m) = 2^(m-1) * n * (-1)^((n-m)/2) * ((n+m)/2-1)! / (((n-m)/2)! * m!) if n>0. - R. J. Mathar, Apr 20 2007
From Paul Weisenhorn, Oct 02 2019: (Start)
T_n(x) = 2*x*T_(n-1)(x) - T_(n-2)(x), T_0(x) = 1, T_1(x) = x.
T_n(x) = ((x+sqrt(x^2-1))^n + (x-sqrt(x^2-1))^n)/2. (End)
From Peter Bala, Aug 15 2022: (Start)
T(n,x) = [z^n] ( z*x + sqrt(1 + z^2*(x^2 - 1)) )^n.
Sum_{k = 0..2*n} binomial(2*n,k)*T(k,x) = (2^n)*(1 + x)^n*T(n,x).
exp( Sum_{n >= 1} T(n,x)*t^n/n ) = Sum_{n >= 0} P(n,x)*t^n, where P(n,x) denotes the n-th Legendre polynomial. (End)

Extensions

Additional comments and more terms from Henry Bottomley, Dec 13 2000
Edited: Corrected Cf. A039991 statement. Cf. A053120 added. - Wolfdieter Lang, Aug 06 2014

A322836 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where A(n,k) is Chebyshev polynomial of the first kind T_{n}(x), evaluated at x=k.

Original entry on oeis.org

1, 1, 0, 1, 1, -1, 1, 2, 1, 0, 1, 3, 7, 1, 1, 1, 4, 17, 26, 1, 0, 1, 5, 31, 99, 97, 1, -1, 1, 6, 49, 244, 577, 362, 1, 0, 1, 7, 71, 485, 1921, 3363, 1351, 1, 1, 1, 8, 97, 846, 4801, 15124, 19601, 5042, 1, 0, 1, 9, 127, 1351, 10081, 47525, 119071, 114243, 18817, 1, -1
Offset: 0

Views

Author

Seiichi Manyama, Dec 28 2018

Keywords

Examples

			Square array begins:
   1, 1,    1,     1,      1,      1,       1, ...
   0, 1,    2,     3,      4,      5,       6, ...
  -1, 1,    7,    17,     31,     49,      71, ...
   0, 1,   26,    99,    244,    485,     846, ...
   1, 1,   97,   577,   1921,   4801,   10081, ...
   0, 1,  362,  3363,  15124,  47525,  120126, ...
  -1, 1, 1351, 19601, 119071, 470449, 1431431, ...
		

Crossrefs

Mirror of A101124.
Main diagonal gives A115066.
Cf. A323182 (Chebyshev polynomial of the second kind).

Programs

  • Mathematica
    Table[ChebyshevT[n-k, k], {n, 0, 10}, {k, n, 0, -1}] // Flatten (* Amiram Eldar, Dec 28 2018 *)
  • PARI
    T(n,k) = polchebyshev(n,1,k);
    matrix(7, 7, n, k, T(n-1,k-1)) \\ Michel Marcus, Dec 28 2018
    
  • PARI
    T(n, k) = round(cos(n*acos(k)));\\ Seiichi Manyama, Mar 05 2021
    
  • PARI
    T(n, k) = if(n==0, 1, n*sum(j=0, n, (2*k-2)^j*binomial(n+j, 2*j)/(n+j))); \\ Seiichi Manyama, Mar 05 2021

Formula

A(0,k) = 1, A(1,k) = k and A(n,k) = 2 * k * A(n-1,k) - A(n-2,k) for n > 1.
A(n,k) = cos(n*arccos(k)). - Seiichi Manyama, Mar 05 2021
A(n,k) = n * Sum_{j=0..n} (2*k-2)^j * binomial(n+j,2*j)/(n+j) for n > 0. - Seiichi Manyama, Mar 05 2021

A322790 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where A(n,k) is Sum_{j=0..k} binomial(2*k,2*j)*(n+1)^(k-j)*n^j.

Original entry on oeis.org

1, 1, 1, 1, 3, 1, 1, 17, 5, 1, 1, 99, 49, 7, 1, 1, 577, 485, 97, 9, 1, 1, 3363, 4801, 1351, 161, 11, 1, 1, 19601, 47525, 18817, 2889, 241, 13, 1, 1, 114243, 470449, 262087, 51841, 5291, 337, 15, 1, 1, 665857, 4656965, 3650401, 930249, 116161, 8749, 449, 17, 1
Offset: 0

Views

Author

Seiichi Manyama, Dec 26 2018

Keywords

Examples

			Square array begins:
   1,  1,   1,    1,      1,       1,         1, ...
   1,  3,  17,   99,    577,    3363,     19601, ...
   1,  5,  49,  485,   4801,   47525,    470449, ...
   1,  7,  97, 1351,  18817,  262087,   3650401, ...
   1,  9, 161, 2889,  51841,  930249,  16692641, ...
   1, 11, 241, 5291, 116161, 2550251,  55989361, ...
   1, 13, 337, 8749, 227137, 5896813, 153090001, ...
		

Crossrefs

Columns 0-3 give A000012, A005408, A069129(n+1), A322830.
Main diagonal gives A173174.
A(n-1,n) gives A173148(n).

Programs

  • Mathematica
    A[0, k_] := 1; A[n_, k_] := Sum[Binomial[2 k, 2 j]*(n + 1)^(k - j)*n^j, {j, 0, k}]; Table[A[n - k, k], {n, 0, 10}, {k, n, 0, -1}] // Flatten (* Amiram Eldar, Dec 26 2018 *)

Formula

a(n) = 2 * A322699(n) + 1.
A(n,k) + sqrt(A(n,k)^2 - 1) = (sqrt(n+1) + sqrt(n))^(2*k).
A(n,k) - sqrt(A(n,k)^2 - 1) = (sqrt(n+1) - sqrt(n))^(2*k).
A(n,0) = 1, A(n,1) = 2*n+1 and A(n,k) = (4*n+2) * A(n,k-1) - A(n,k-2) for k > 1.
A(n,k) = T_{k}(2*n+1) where T_{k}(x) is a Chebyshev polynomial of the first kind.
T_1(x) = x. So A(n,1) = 2*n+1.

A133285 Indices of the centered 12-gonal numbers which are also 12-gonal number, or numbers X such that 120*X^2-120*X+36 is a square.

Original entry on oeis.org

1, 12, 253, 5544, 121705, 2671956, 58661317, 1287877008, 28274632849, 620754045660, 13628314371661, 299202162130872, 6568819252507513, 144214821393034404, 3166157251394249365, 69511244709280451616
Offset: 1

Views

Author

Richard Choulet, Oct 16 2007

Keywords

Comments

Partial sums of A077422. - R. J. Mathar, Nov 27 2011
Indices of centered pentagonal numbers (A005891) which are also centered hexagonal numbers (A003215). - Colin Barker, Feb 07 2015

Crossrefs

Programs

Formula

a(n+2) = 22*a(n+1)-a(n)-10 ; a(n+1)=11*a(n)-5+(120*a(n)^2-120*a(n)+36)^0.5
G.f. x*(-1+11*x) / ( (x-1)*(x^2-22*x+1) ). - R. J. Mathar, Nov 27 2011

Extensions

More terms from Paolo P. Lava, Aug 06 2008

A090730 a(n) = 22*a(n-1) - a(n-2), starting with a(0) = 2 and a(1) = 22.

Original entry on oeis.org

2, 22, 482, 10582, 232322, 5100502, 111978722, 2458431382, 53973511682, 1184958825622, 26015120652002, 571147695518422, 12539234180753282, 275292004281053782, 6043884860002429922, 132690174915772404502
Offset: 0

Views

Author

Nikolay V. Kosinov (kosinov(AT)unitron.com.ua), Jan 18 2004

Keywords

Crossrefs

Programs

  • Mathematica
    a[0] = 2; a[1] = 22; a[n_] := 22a[n - 1] - a[n - 2]; Table[ a[n], {n, 0, 15}] (* Robert G. Wilson v, Jan 30 2004 *)
    LinearRecurrence[{22,-1},{2,22},20] (* Harvey P. Dale, Mar 07 2018 *)
  • Sage
    [lucas_number2(n,22,1) for n in range(0,20)] # Zerinvary Lajos, Jun 26 2008

Formula

a(n) = p^n + q^n, where p = 11 + 2*sqrt(30) and q = 11 - 2*sqrt(30). - Tanya Khovanova, Feb 06 2007
G.f.: (2-22*x)/(1-22*x+x^2). - Philippe Deléham, Nov 18 2008
a(n) = 2*A077422(n). - R. J. Mathar, Sep 27 2014

A322707 a(0)=0, a(1)=5 and a(n) = 22*a(n-1) - a(n-2) + 10 for n > 1.

Original entry on oeis.org

0, 5, 120, 2645, 58080, 1275125, 27994680, 614607845, 13493377920, 296239706405, 6503780163000, 142786923879605, 3134808545188320, 68823001070263445, 1510971215000607480, 33172543728943101125, 728284990821747617280, 15989097254349504479045
Offset: 0

Views

Author

Seiichi Manyama, Dec 24 2018

Keywords

Comments

Solutions to X*(X+1)=30*Y^2 with Y=A077421. - R. J. Mathar, Mar 14 2023

Examples

			(sqrt(6) + sqrt(5))^2 = 11 + 2*sqrt(30) = sqrt(121) + sqrt(120). So a(2) = 120.
		

Crossrefs

Row 5 of A322699.
Cf. A188930 (sqrt(5)+sqrt(6)).

Programs

  • PARI
    concat(0, Vec(5*x*(1 + x) / ((1 - x)*(1 - 22*x + x^2)) + O(x^20))) \\ Colin Barker, Dec 24 2018

Formula

sqrt(a(n)+1) + sqrt(a(n)) = (sqrt(6) + sqrt(5))^n.
sqrt(a(n)+1) - sqrt(a(n)) = (sqrt(6) - sqrt(5))^n.
a(n) = 23*a(n-1) - 23*a(n-2) + a(n-3) for n > 2.
From Colin Barker, Dec 24 2018: (Start)
G.f.: 5*x*(1 + x) / ((1 - x)*(1 - 22*x + x^2)).
a(n) = ((11+2*sqrt(30))^(-n) * (-1+(11+2*sqrt(30))^n)^2) / 4.
(End)
2*a(n) = A077422(n)-1. - R. J. Mathar, Mar 16 2023

A238245 Positive integers n such that x^2 - 22xy + y^2 + n = 0 has integer solutions.

Original entry on oeis.org

20, 39, 56, 71, 80, 84, 95, 104, 111, 116, 119, 120, 156, 180, 191, 224, 239, 255, 284, 296, 311, 320, 336, 351, 359, 380, 399, 404, 416, 431, 444, 455, 464, 471, 476, 479, 480, 500, 504, 551, 596, 599, 624, 639, 680, 695, 696, 719, 720, 756, 764, 791, 824
Offset: 1

Views

Author

Colin Barker, Feb 20 2014

Keywords

Examples

			39 is in the sequence because x^2 - 22xy + y^2 + 39 = 0 has integer solutions, for example (x, y) = (2, 43).
		

Crossrefs

Cf. A157014 (n = 20), A137881 (n = 104), A077422 (n = 120), A133275 (n = 180).

A099278 Unsigned member r=-20 of the family of Chebyshev sequences S_r(n) defined in A092184.

Original entry on oeis.org

0, 1, 20, 441, 9680, 212521, 4665780, 102434641, 2248896320, 49373284401, 1083963360500, 23797820646601, 522468090864720, 11470500178377241, 251828535833434580, 5528757288157183521, 121380831803624602880
Offset: 0

Views

Author

Wolfdieter Lang, Oct 18 2004

Keywords

Comments

((-1)^(n+1))*a(n) = S_{-20}(n), n>=0, defined in A092184.

Formula

a(n)= (T(n, 11)-(-1)^n)/12, with Chebyshev's polynomials of the first kind evaluated at x=11: T(n, 11)=A077422(n)=((11+2*sqrt(30))^n + (11-2*sqrt(30))^n)/2.
a(n)= 22*a(n-1)-a(n-2)+2*(-1)^(n+1), n>=2, a(0)=0, a(1)=1.
a(n)= 21*a(n-1) + 21*a(n-2) - a(n-3), n>=3, a(0)=0, a(1)=1, a(2)=20.
G.f.: x*(1-x)/((1+x)*(1-22*x+x^2)) = x*(1-x)/(1-21*x-21*x^2+x^3) (from the Stephan link, see A092184).
Showing 1-9 of 9 results.