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.

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A022168 Triangle of Gaussian binomial coefficients [ n,k ] for q = 4.

Original entry on oeis.org

1, 1, 1, 1, 5, 1, 1, 21, 21, 1, 1, 85, 357, 85, 1, 1, 341, 5797, 5797, 341, 1, 1, 1365, 93093, 376805, 93093, 1365, 1, 1, 5461, 1490853, 24208613, 24208613, 1490853, 5461, 1, 1, 21845, 23859109, 1550842085, 6221613541
Offset: 0

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Author

Keywords

Comments

The coefficients of the matrix inverse are apparently given by T^(-1)(n,k) = (-1)^n*A157784(n,k). - R. J. Mathar, Mar 12 2013

Examples

			Triangle begins:
  1;
  1,    1;
  1,    5,       1;
  1,   21,      21,        1;
  1,   85,     357,       85,        1;
  1,  341,    5797,     5797,      341,       1;
  1, 1365,   93093,   376805,    93093,    1365,    1;
  1, 5461, 1490853, 24208613, 24208613, 1490853, 5461, 1;
		

References

  • F. J. MacWilliams and N. J. A. Sloane, The Theory of Error-Correcting Codes, Elsevier-North Holland, 1978, p. 698.

Crossrefs

Cf. A006118 (row sums), A002450 (k=1), A006105 (k=2), A006106 (k=3).

Programs

  • Maple
    A022168 := proc(n,m)
            A027637(n)/A027637(n-m)/A027637(m) ;
    end proc: # R. J. Mathar, Nov 14 2011
  • Mathematica
    gaussianBinom[n_, k_, q_] := Product[q^i - 1, {i, n}]/Product[q^j - 1, {j, n - k}]/Product[q^l - 1, {l, k}]; Column[Table[gaussianBinom[n, k, 4], {n, 0, 8}, {k, 0, n}], Center] (* Alonso del Arte, Nov 14 2011 *)
    Table[QBinomial[n,k,4], {n,0,10}, {k,0,n}]//Flatten (* or *) q:= 4; T[n_, 0]:= 1; T[n_,n_]:= 1; T[n_,k_]:= T[n,k] = If[k < 0 || n < k, 0, T[n-1, k -1] +q^k*T[n-1,k]]; Table[T[n,k], {n,0,10}, {k,0,n}] // Flatten  (* G. C. Greubel, May 27 2018 *)
  • PARI
    {q=4; T(n,k) = if(k==0,1, if (k==n, 1, if (k<0 || nG. C. Greubel, May 27 2018

Formula

T(n,k) = T(n-1,k-1) + q^k * T(n-1,k). - Peter A. Lawrence, Jul 13 2017
G.f. of column k: x^k * exp( Sum_{j>=1} f((k+1)*j)/f(j) * x^j/j ), where f(j) = 4^j - 1. - Seiichi Manyama, May 09 2025

A006096 Gaussian binomial coefficient [n, 3] for q = 2.

Original entry on oeis.org

1, 15, 155, 1395, 11811, 97155, 788035, 6347715, 50955971, 408345795, 3269560515, 26167664835, 209386049731, 1675267338435, 13402854502595, 107225699266755, 857817047249091, 6862582190715075, 54900840777134275, 439207459223777475
Offset: 3

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Author

Keywords

Comments

42*a(n) is a maximum number of intercalates in a Latin square of order 2^n-1 (see A092237). - Eduard I. Vatutin, Apr 24 2025

References

  • J. Goldman and G.-C. Rota, The number of subspaces of a vector space, pp. 75-83 of W. T. Tutte, editor, Recent Progress in Combinatorics. Academic Press, NY, 1969.
  • I. P. Goulden and D. M. Jackson, Combinatorial Enumeration. Wiley, NY, 1983, p. 99.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • M. Sved, Gaussians and binomials, Ars. Combinatoria, 17A (1984), 325-351.

Crossrefs

Gaussian binomial coefficient [n, k] for q = 2: A000225 (k = 1), A006095 (k = 2), this sequence (k = 3), A006097 (k = 4), A006110 (k = 5), A022189 - A022195 (k = 6 thru 12).
Cf. A092237.

Programs

  • Magma
    r:=3; q:=2; [&*[(1-q^(n-i+1))/(1-q^i): i in [1..r]]: n in [r..25]]; // Vincenzo Librandi, Nov 06 2016
  • Maple
    seq((-1+7*2^n-14*4^n+8*8^n)/21,n=1..20);
    A006096:=1/(z-1)/(8*z-1)/(2*z-1)/(4*z-1); # Simon Plouffe in his 1992 dissertation with offset 0
  • Mathematica
    Drop[CoefficientList[Series[x^3/((1 - x) (1 - 2 x) (1 - 4 x) (1 - 8 x)), {x, 0, 30}], x], 3]
    QBinomial[Range[3,30],3,2] (* Harvey P. Dale, Jan 28 2013 *)
  • Sage
    [gaussian_binomial(n,3,2) for n in range(3,23)] # Zerinvary Lajos, May 24 2009
    

Formula

G.f.: x^3/((1-x)(1-2x)(1-4x)(1-8x)).
(With a different offset) a(n) = (-1+7*2^n-14*4^n+8*8^n)/21. - James R. Buddenhagen, Dec 14 2003
From Peter Bala, Jul 01 2025: (Start)
a(n) = (q^n - 1)*(q^(n-1) - 1)*(q^(n-2) - 1)/((q^3 - 1)*(q^2 - 1)*(q - 1)) at q = 2.
G.f. with an offset of 0: exp( Sum_{n >= 1} b(4*n)/b(n)*x^n/n ) = 1 + 15*x + 155*x^2 + ..., where b(n) = A000225(n) = 2^n - 1.
The following series telescope:
Sum_{n >= 3} 2^n/(a(n)*a(n+3)) = 420/72075;
Sum_{n >= 3} 4^n/(a(n)*a(n+3)) = 3416/72075;
Sum_{n >= 3} 8^n/(a(n)*a(n+3)) = 28296/72075;
Sum_{n >= 3} 16^n/(a(n)*a(n+3)) = 244748/72075;
Sum_{n >= 3} 32^n/(a(n)*a(n+3)) = 2415315/72075. (End)

A006097 Gaussian binomial coefficient [n, 4] for q = 2.

Original entry on oeis.org

1, 31, 651, 11811, 200787, 3309747, 53743987, 866251507, 13910980083, 222984027123, 3571013994483, 57162391576563, 914807651274739, 14638597687734259, 234230965858250739, 3747802679431278579, 59965700687947706355, 959458073589354016755, 15351384078270441402355
Offset: 4

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Author

Keywords

References

  • J. Goldman and G.-C. Rota, The number of subspaces of a vector space, pp. 75-83 of W. T. Tutte, editor, Recent Progress in Combinatorics. Academic Press, NY, 1969.
  • I. P. Goulden and D. M. Jackson, Combinatorial Enumeration. Wiley, NY, 1983, p. 99.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • M. Sved, Gaussians and binomials, Ars. Combinatoria, 17A (1984), 325-351.

Crossrefs

Gaussian binomial coefficient [n, k] for q = 2: A000225 (k = 1), A006095 (k = 2), A006096 (k = 3), this sequence (k = 4), A006110 (k = 5), A022189 - A022195 (k = 6 thru 12).

Programs

  • Magma
    r:=4; q:=2; [&*[(1-q^(n-i+1))/(1-q^i): i in [1..r]]: n in [r..25]]; // Vincenzo Librandi, Nov 06 2016
    
  • Maple
    A006097:=-1/(z-1)/(4*z-1)/(2*z-1)/(8*z-1)/(16*z-1); # Simon Plouffe in his 1992 dissertation with offset 0
  • Mathematica
    faq[n_, q_] = Product[(1-q^(1+k))/(1-q), {k, 0, n-1}];
    qbin[n_, m_, q_] = faq[n, q]/(faq[m, q]*faq[n-m, q]);
    Table[qbin[n, 4, 2], {n, 4, 21}] (* Jean-François Alcover, Jul 21 2011 *)
    QBinomial[Range[4,30],4,2] (* Harvey P. Dale, Dec 10 2012 *)
  • PARI
    a(n)=(2^n-1)*(2^n-2)*(2^n-4)*(2^n-8)/20160 \\ Charles R Greathouse IV, Feb 19 2017
  • Sage
    [gaussian_binomial(n,4,2) for n in range(4,22)] # Zerinvary Lajos, May 24 2009
    

Formula

G.f.: x^4/((1-x)*(1-2*x)*(1-4*x)*(1-8*x)*(1-16*x)).
a(n) = (2^n-1)*(2^n-2)*(2^n-4)*(2^n-8)/20160. - Bruno Berselli, Aug 29 2011
From Peter Bala, Jul 01 2025: (Start)
G.f. with an offset of 0: exp( Sum_{n >= 1} b(5*n)/b(n)*x^n/n ) = 1 + 31*x + 651*x^2 + ..., where b(n) = A000225(n) = 2^n - 1.
The following series telescope:
Sum_{n >= 4} 2^n/a(n) = 120/7; Sum_{n >= 4} 4^n/a(n) = 2078/7;
Sum_{n >= 4} 8^n/a(n) = 41280/7.
Sum_{n >= 4} 2^n/(a(n)*a(n+4)) = 40/499999;
Sum_{n >= 4} 2^n/(a(n)*a(n+4)*a(n+8)) = 40/6981154678721773;
Sum_{n >= 4} 2^n/(a(n)*a(n+4)*a(n+8)*a(n+12)) = 40/6387876185324781622646124392439. (End)

A006110 Gaussian binomial coefficient [n, 5] for q = 2.

Original entry on oeis.org

1, 63, 2667, 97155, 3309747, 109221651, 3548836819, 114429029715, 3675639930963, 117843461817939, 3774561792168531, 120843139740969555, 3867895279362300499, 123787287537281350227, 3961427432158861458003, 126769425631762997934675, 4056681585917103881615955, 129814770207420913565727315
Offset: 5

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Author

Keywords

References

  • J. Goldman and G.-C. Rota, The number of subspaces of a vector space, pp. 75-83 of W. T. Tutte, editor, Recent Progress in Combinatorics. Academic Press, NY, 1969.
  • I. P. Goulden and D. M. Jackson, Combinatorial Enumeration. Wiley, NY, 1983, p. 99.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • M. Sved, Gaussians and binomials, Ars. Combinatoria, 17A (1984), 325-351.

Crossrefs

Gaussian binomial coefficient [n, k] for q = 2: A000225 (k = 1), A006095 (k = 2), A006096 (k = 3), A006097 (k = 4), this sequence (k = 5), A022189 - A022195 ( k = 6 thru 12).

Programs

  • Magma
    r:=5; q:=2; [&*[(1-q^(n-i+1))/(1-q^i): i in [1..r]]: n in [r..20]]; // Vincenzo Librandi, Aug 07 2016
  • Maple
    seq((1024*32^n-1984*16^n+1240*8^n-310*4^n+31*2^n-1)/9765,n=1..20);
    A006110:=1/(z-1)/(4*z-1)/(2*z-1)/(8*z-1)/(16*z-1)/(32*z-1); # Simon Plouffe in his 1992 dissertation with offset 0
  • Mathematica
    Table[QBinomial[n, 5, 2], {n, 5, 20}] (* Vincenzo Librandi, Aug 07 2016 *)
  • Sage
    [gaussian_binomial(n,5,2) for n in range(5,18)] # Zerinvary Lajos, May 24 2009
    

Formula

a(n+4) = (1024*32^n-1984*16^n+1240*8^n-310*4^n+31*2^n-1)/9765. - James R. Buddenhagen, Dec 14 2003
G.f.: x^5/((1-x)*(1-2*x)*(1-4*x)*(1-8*x)*(1-16*x)*(1-32*x)). - Vincenzo Librandi, Aug 07 2016
a(n) = Product_{i=1..5} (2^(n-i+1)-1)/(2^i-1), by definition. - Vincenzo Librandi, Aug 06 2016
a(n) = (2^n-16)*(2^n-8)*(2^n-4)*(2^n-2)*(2^n-1)/9999360. - Robert Israel, Feb 01 2018
G.f. with an offset of 0: exp( Sum_{n >= 1} b(6*n)/b(n)*x^n/n ) = 1 + 63*x + 2667*x^2 + ..., where b(n) = A000225(n) = 2^n - 1. - Peter Bala, Jul 01 2025

A022189 Gaussian binomial coefficients [n, 6] for q = 2.

Original entry on oeis.org

1, 127, 10795, 788035, 53743987, 3548836819, 230674393235, 14877590196755, 955841412523283, 61291693863308051, 3926442969043883795, 251413193158549532435, 16094312257426532376339, 1030159771762835353435923
Offset: 6

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Crossrefs

Gaussian binomial coefficient [n, k] for q = 2: A000225 (k = 1), A006095 (k = 2), A006096 (k = 3), A006097 (k = 4), A006110 (k = 5), this sequence (k = 6), A022190 - A022195 (k = 7 thru 12).

Programs

  • Magma
    r:=6; q:=2; [&*[(1-q^(n-i+1))/(1-q^i): i in [1..r]]: n in [r..20]]; // Vincenzo Librandi, Aug 03 2016
    
  • Mathematica
    Table[QBinomial[n, 6, 2], {n, 6, 24}] (* Vincenzo Librandi, Aug 03 2016 *)
  • PARI
    r=6; q=2; for(n=r,30, print1(prod(j=1,r,(1-q^(n-j+1))/(1-q^j)), ", ")) \\ G. C. Greubel, May 30 2018
  • Sage
    [gaussian_binomial(n,6,2) for n in range(6,20)] # Zerinvary Lajos, May 24 2009
    

Formula

a(n) = Product_{i=1..6} (2^(n-i+1)-1)/(2^i-1), by definition. - Vincenzo Librandi, Aug 03 2016
G.f. with an offset of 0: exp( Sum_{n >= 1} b(7*n)/b(n)*x^n/n ) = 1 + 127*x + 10795*x^2 + ..., where b(n) = A000225(n) = 2^n - 1. - Peter Bala, Jul 01 2025

Extensions

Offset changed by Vincenzo Librandi, Aug 03 2016

A022195 Gaussian binomial coefficients [n, 12] for q = 2.

Original entry on oeis.org

1, 8191, 44731051, 209386049731, 914807651274739, 3867895279362300499, 16094312257426532376339, 66441249531569955747981459, 273210326382611632738979052435, 1121258922081448861468067825426835, 4597164868683271949171164500871212435
Offset: 12

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Author

Keywords

References

  • F. J. MacWilliams and N. J. A. Sloane, The Theory of Error-Correcting Codes, Elsevier-North Holland, 1978, p. 698.

Crossrefs

Gaussian binomial coefficient [n, k] for q = 2: A000225 (k = 1), A006095 (k = 2), A006096 (k = 3), A006097 (k = 4), A006110 (k = 5), A022189 - A022194 (k = 6 thru 11).

Programs

  • Magma
    r:=12; q:=2; [&*[(1-q^(n-i+1))/(1-q^i): i in [1..r]]: n in [r..25]]; // Vincenzo Librandi, Aug 03 2016
    
  • Mathematica
    Table[QBinomial[n, 12, 2], {n, 12, 200}] (* Vincenzo Librandi, Aug 03 2016 *)
  • PARI
    r=12; q=2; for(n=r,30, print1(prod(j=1,r,(1-q^(n-j+1))/(1-q^j)), ", ")) \\ G. C. Greubel, May 30 2018
  • Sage
    [gaussian_binomial(n,12,2) for n in range(12,23)] # Zerinvary Lajos, May 25 2009
    

Formula

a(n) = Product_{i=1..12} (2^(n-i+1)-1)/(2^i-1), by definition. - Vincenzo Librandi, Aug 03 2016
G.f. assuming an offset of 0: exp( Sum_{n >= 1} b(13*n)/b(n)*x^n/n ) = 1 + 8191*x + 44731051*x^2 + ..., where b(n) = A000225(n) = 2^n - 1. - Peter Bala, Jul 03 2025

Extensions

Offset changed by Vincenzo Librandi, Aug 03 2016

A060487 Triangle T(n,k) of k-block tricoverings of an n-set (n >= 3, k >= 4).

Original entry on oeis.org

1, 3, 1, 7, 57, 95, 43, 3, 35, 717, 3107, 4520, 2465, 445, 12, 155, 7845, 75835, 244035, 325890, 195215, 50825, 4710, 70, 651, 81333, 1653771, 10418070, 27074575, 33453959, 20891962, 6580070, 965965, 52430, 465
Offset: 3

Views

Author

Vladeta Jovovic, Mar 20 2001

Keywords

Comments

A covering of a set is a tricovering if every element of the set is covered by exactly three blocks of the covering.

Examples

			Triangle begins:
  [1, 3, 1];
  [7, 57, 95, 43, 3];
  [35, 717, 3107, 4520, 2465, 445, 12];
  [155, 7845, 75835, 244035, 325890, 195215, 50825, 4710, 70];
  [651, 81333, 1653771, 10418070, 27074575, 33453959, 20891962, 6580070, 965965, 52430, 465];
   ...
There are 205 tricoverings of a 4-set(cf. A060486): 7 4-block, 57 5-block, 95 6-block, 43 7-block and 3 8-block tricoverings.
		

Crossrefs

Programs

  • PARI
    WeighT(v)={Vec(exp(x*Ser(dirmul(v, vector(#v, n, (-1)^(n-1)/n))))-1, -#v)}
    D(p, n, k)={my(v=vector(n)); for(i=1, #p, v[p[i]]++); WeighT(v)[n]^k/prod(i=1, #v, i^v[i]*v[i]!)}
    row(n, k)={my(m=n*k+1, q=Vec(exp(intformal(O(x^m) - x^n/(1-x)))/(y+x))); if(n==0, 1, (-1)^m*sum(j=0, m, my(s=0); forpart(p=j, s+=(-1)^#p*D(p, n, k), [1, n]); s*q[#q-j])*y^(m-n)/(1+y))}
    for(n=3, 8, print(Vecrev(row(3,n)))); \\ Andrew Howroyd, Dec 23 2018

Formula

E.g.f. for k-block tricoverings of an n-set is exp(-x+x^2/2+(exp(y)-1)*x^3/3)*Sum_{k=0..inf}x^k/k!*exp(-1/2*x^2*exp(k*y))*exp(binomial(k, 3)*y).

A006100 Gaussian binomial coefficient [n, 2] for q = 3.

Original entry on oeis.org

1, 13, 130, 1210, 11011, 99463, 896260, 8069620, 72636421, 653757313, 5883904390, 52955405230, 476599444231, 4289397389563, 38604583680520, 347441274648040, 3126971536402441
Offset: 2

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Author

Keywords

References

  • J. Goldman and G.-C. Rota, The number of subspaces of a vector space, pp. 75-83 of W. T. Tutte, editor, Recent Progress in Combinatorics. Academic Press, NY, 1969.
  • I. P. Goulden and D. M. Jackson, Combinatorial Enumeration. Wiley, NY, 1983, p. 99.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • M. Sved, Gaussians and binomials, Ars. Combinatoria, 17A (1984), 325-351.

Crossrefs

Cf. A203243.

Programs

  • Maple
    a:=n->sum((9^(n-j)-3^(n-j))/6,j=0..n): seq(a(n), n=1..17); # Zerinvary Lajos, Jan 15 2007
    A006100:=-1/(z-1)/(3*z-1)/(9*z-1); # Simon Plouffe in his 1992 dissertation with offset 0
  • Mathematica
    f[k_] := 3^(k - 1); t[n_] := Table[f[k], {k, 1, n}]
    a[n_] := SymmetricPolynomial[2, t[n]]
    Table[a[n], {n, 2, 32}]    (* A203243 *)
    Table[a[n]/3, {n, 2, 32}]  (* A006100 *)
  • Sage
    [gaussian_binomial(n,2,3) for n in range(2,19)] # Zerinvary Lajos, May 25 2009

Formula

G.f.: x^2/[(1-x)(1-3x)(1-9x)].
a(n) = (9^n - 4*3^n + 3)/48. - Mitch Harris, Mar 23 2008
a(n) = 4*a(n-1) -3*a(n-2) +9^(n-2), n>=4. - Vincenzo Librandi, Mar 20 2011
From Peter Bala, Jul 01 2025: (Start)
G.f. with an offset of 0: exp(Sum_{n >= 1} b(3*n)/b(n)*x^n/n) = 1 + 13*x + 130*x^2 + ..., where b(n) = 3^n - 1.
The following series telescope:
Sum_{n >= 2} 3^n/a(n) = 12; Sum_{n >= 2} 3^n/(a(n)*a(n+3)) = 129/16900;
Sum_{n >= 2} 9^n/(a(n)*a(n+3)) = 1227/16900;
Sum_{n >= 2} 3^n/(a(n)*a(n+3)*a(n+6)) = 156706257/18829431219368770. (End)

A006105 Gaussian binomial coefficient [ n,2 ] for q=4.

Original entry on oeis.org

1, 21, 357, 5797, 93093, 1490853, 23859109, 381767589, 6108368805, 97734250405, 1563749404581, 25019996065701, 400319959420837, 6405119440211877, 102481911401303973
Offset: 2

Views

Author

Keywords

References

  • J. Goldman and G.-C. Rota, The number of subspaces of a vector space, pp. 75-83 of W. T. Tutte, editor, Recent Progress in Combinatorics. Academic Press, NY, 1969.
  • I. P. Goulden and D. M. Jackson, Combinatorial Enumeration. Wiley, NY, 1983, p. 99.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • M. Sved, Gaussians and binomials, Ars. Combinatoria, 17A (1984), 325-351.

Programs

  • Maple
    A006105:=-1/(z-1)/(4*z-1)/(16*z-1); # Simon Plouffe in his 1992 dissertation, assuming offset zero
  • Mathematica
    faq[n_, q_] = Product[(1-q^(1+k))/(1-q), {k, 0, n-1}];
    qbin[n_, m_, q_] = faq[n, q]/(faq[m, q]*faq[n-m, q]);
    Table[qbin[n, 2, 4], {n, 2, 16}] (* Jean-François Alcover, Jul 21 2011 *)
    CoefficientList[Series[1 / ((1 - x) (1 - 4 x) (1 - 16 x)), {x, 0, 40}], x] (* Vincenzo Librandi, Jul 23 2013 *)
    LinearRecurrence[{21,-84,64},{1,21,357},20] (* Harvey P. Dale, Feb 17 2020 *)
  • Sage
    [gaussian_binomial(n,2,4) for n in range(2,17)] # Zerinvary Lajos, May 28 2009

Formula

G.f.: x^2/((1-x)*(1-4*x)*(1-16*x)). [Multiplied by x^2 to match offset by R. J. Mathar, Mar 11 2009]
a(n) = (16^n - 5*4^n + 4)/180. - Mitch Harris, Mar 23 2008
a(n) = 5*a(n-1) -4*a(n-2) +16^(n-2), n>=4. - Vincenzo Librandi, Mar 20 2011

A006117 Sum of Gaussian binomial coefficients [ n,k ] for q=3.

Original entry on oeis.org

1, 2, 6, 28, 212, 2664, 56632, 2052656, 127902864, 13721229088, 2544826627424, 815300788443072, 452436459318538048, 434188323928823259776, 722197777341507864283008, 2078153254879878944892861184, 10366904326991986000747424911616, 89478415088556766546699920236339712, 1338962661056423158371347974009398601216
Offset: 0

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Author

Keywords

Examples

			O.g.f.: A(x) = 1/(1-x) + x/((1-x)*(1-3x)) + x^2/((1-x)*(1-3x)*(1-9x)) + x^3/((1-x)*(1-3x)*(1-9x)*(1-27x)) + ...
Also generated by iterated binomial transforms in the following way:
[1,2,6,28,212,2664,56632,...] = BINOMIAL([1,1,3,15,129,1833,43347,..]);
[1,3,15,129,1833,43347,1705623,...] = BINOMIAL^2([1,1,7,67,1081,...]);
[1,7,67,1081,29185,1277887,...] = BINOMIAL^6([1,1,19,415,12961,...]);
[1,19,415,12961,684361,58352707,...] = BINOMIAL^18([1,1,55,3187,...]);
[1,55,3187,219673,22634209,...] = BINOMIAL^54([1,1,163,27055,4805569,...]);
etc.
G.f. = 1 + 2*x + 6*x^2 + 28*x^3 + 212*x^4 + 2664*x^5 + 56632*x^6 + 2052656*x^7 + ...
		

References

  • J. Goldman and G.-C. Rota, The number of subspaces of a vector space, pp. 75-83 of W. T. Tutte, editor, Recent Progress in Combinatorics. Academic Press, NY, 1969.
  • I. P. Goulden and D. M. Jackson, Combinatorial Enumeration. Wiley, NY, 1983, p. 99.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • M. Sved, Gaussians and binomials, Ars. Combinatoria, 17A (1984), 325-351.

Programs

  • Magma
    [n le 2 select n else 2*Self(n-1)+(3^(n-2)-1)*Self(n-2): n in [1..40]]; // Vincenzo Librandi, Aug 13 2016
  • Maple
    f:=n-> 1+ add( mul((3^(n-i)-1)/(3^(i+1)-1), i=0..k-1), k=1..n);
  • Mathematica
    Flatten[{1,RecurrenceTable[{a[n]==2*a[n-1]+(3^(n-1)-1)*a[n-2],a[0]==1,a[1]==2},a,{n,1,15}]}] (* Vaclav Kotesovec, Aug 21 2013 *)
    Table[Sum[QBinomial[n, k, 3], {k, 0, n}], {n, 0, 20}] (* Vincenzo Librandi, Aug 13 2016 *)
  • PARI
    a(n)=polcoeff(sum(k=0, n, x^k/prod(j=0, k, 1-3^j*x+x*O(x^n))), n) \\ Paul D. Hanna, Dec 06 2007
    

Formula

O.g.f.: A(x) = Sum_{n>=0} x^n / Product_{k=0..n} (1 - 3^k*x). - Paul D. Hanna, Dec 06 2007
a(n) = 2*a(n-1)+(3^(n-1)-1)*a(n-2), n>1. [Hitzemann and Hochstattler] - R. J. Mathar, Aug 21 2013
a(n) ~ c * 3^(n^2/4), where c = EllipticTheta[3,0,1/3] / QPochhammer[1/3,1/3] = 3.019783845699... if n is even and c = EllipticTheta[2,0,1/3]/QPochhammer[1/3,1/3] = 3.018269046371... if n is odd. - Vaclav Kotesovec, Aug 21 2013
0 = a(n)*(2*a(n+1) + 2*a(n+2) - a(n+3)) + a(n+1)*(-6*a(n+1) + 3*a(n+2)) for all n in Z. - Michael Somos, Jan 25 2014
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