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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A157785 Triangle of coefficients of the polynomials defined by q^binomial(n, 2)*QPochhammer(x, 1/q, n), where q = -2.

Original entry on oeis.org

1, 1, -1, -2, 1, 1, -8, 6, 3, -1, 64, -40, -30, 5, 1, 1024, -704, -440, 110, 11, -1, -32768, 21504, 14784, -3080, -462, 21, 1, -2097152, 1409024, 924672, -211904, -26488, 1806, 43, -1, 268435456, -178257920, -119767040, 26199040, 3602368, -204680, -7310, 85, 1
Offset: 0

Views

Author

Roger L. Bagula, Mar 06 2009

Keywords

Comments

Triangle T(n,k), 0 <= k <= n, read by rows given by [1, q-1, q^2, q^3-q, q^4, q^5-q^2, q^6, q^7-q^3, q^8, ...] DELTA [-1, 0, -q, 0, -q^2, 0, -q^3, 0, -q^4, 0, ...] (for q=-2) = [1, -3, 4, -6, 16, -36, 64,...] DELTA [ -1, 0, 2, 0, -4, 0, 8, 0, -16, 0, ...] where DELTA is the operator defined in A084938. - Philippe Deléham, Mar 10 2009

Examples

			Triangle begins as:
          1;
          1,         -1;
         -2,          1,          1;
         -8,          6,          3,       -1;
         64,        -40,        -30,        5,       1;
       1024,       -704,       -440,      110,      11,      -1;
     -32768,      21504,      14784,    -3080,    -462,      21,     1;
   -2097152,    1409024,     924672,  -211904,  -26488,    1806,    43, -1;
  268435456, -178257920, -119767040, 26199040, 3602368, -204680, -7310, 85, 1;
		

Crossrefs

Cf. this sequence (q=-2), A158020 (q=-1), A007318 (q=1), A157963 (q=2).
Cf. A135950 (q=2; alternative).

Programs

  • Mathematica
    p[x_, n_, q_]:= q^Binomial[n, 2]*QPochhammer[x, 1/q, n];
    Table[CoefficientList[Series[p[x, n, -2], {x,0,n}], x], {n,0,10}]//Flatten (* G. C. Greubel, Nov 29 2021 *)

Formula

Sum_{k=0..n} T(n, k) = 0^n.
From G. C. Greubel, Nov 29 2021: (Start)
T(n, k) = [x^k] coefficients of the polynomials defined by q^binomial(n, 2)*QPochhammer(x, 1/q, n), where q = -2.
T(n, k) = [x^k] Product_{j=0..n-1} (q^j - x). (End)

Extensions

Edited by G. C. Greubel, Nov 29 2021

A157963 Triangle T(n,k), 0<=k<=n, read by rows given by [1,q-1,q^2,q^3-q,q^4,q^5-q^2,q^6,q^7-q^3,q^8,...] DELTA [ -1,0,-q,0,-q^2,0,-q^3,0,-q^4,0,-q^5,0,...] (for q=2) = [1,1,4,6,16,28,64,...] DELTA [ -1,0,-2,0,-4,0,-8,0,-16,0,...] where DELTA is the operator defined in A084938.

Original entry on oeis.org

1, 1, -1, 2, -3, 1, 8, -14, 7, -1, 64, -120, 70, -15, 1, 1024, -1984, 1240, -310, 31, -1, 32768, -64512, 41664, -11160, 1302, -63, 1, 2097152, -4161536, 2731008, -755904, 94488, -5334, 127, -1, 268435456, -534773760, 353730560, -99486720, 12850368
Offset: 0

Views

Author

Philippe Deléham, Mar 10 2009

Keywords

Comments

Row sums equal 0^n.
Row n contains the coefficients of Product_{j=0..n-1} (2^j*x-1), highest coefficient first. - Alois P. Heinz, Mar 26 2012
The elements of the matrix inverse are apparently given by T^(-1)(n,k) = (-1)^k*A022166(n,k). - R. J. Mathar, Mar 26 2013

Examples

			Triangle begins :
1;
1,    -1;
2,    -3,  1;
8,   -14,  7,  -1;
64, -120, 70, -15,  1;
		

Crossrefs

Programs

  • Maple
    T:= n-> seq (coeff (mul (2^j*x-1, j=0..n-1), x, n-k), k=0..n):
    seq (T(n), n=0..10);  # Alois P. Heinz, Mar 26 2012
  • Mathematica
    row[n_] := CoefficientList[(-1)^n QPochhammer[x, 2, n] + O[x]^(n+1), x] // Reverse; Table[row[n], {n, 0, 10}] // Flatten (* Jean-François Alcover, May 26 2016 *)

Formula

T(n,k) = (-1)^n*A135950(n,k). T(n,0) = A006125(n).
T(n,k) = [x^(n-k)] Product_{j=0..n-1} (2^j*x-1). - Alois P. Heinz, Mar 26 2012

A218449 Gaussian binomial coefficient [2*n-1,n] for q=2, n>=0.

Original entry on oeis.org

1, 1, 7, 155, 11811, 3309747, 3548836819, 14877590196755, 246614610741341843, 16256896431763117598611, 4274137206973266943778085267, 4488323837657412597958687922896275, 18839183877670041942218307147122500601235
Offset: 0

Views

Author

Paul D. Hanna, Oct 28 2012

Keywords

Comments

Compare to: [x^n] Product_{k=0..n-1} 1+2^k*x = 2^(n*(n-1)/2).

Examples

			The coefficients in Product_{k=0..n-1} 1/(1 - 2^k*x) begin:
n=0: [(1)];
n=1: [1,(1), 1, 1, 1, 1, 1, 1, 1, 1, ...];
n=2: [1, 3,(7), 15, 31, 63, 127, 255, 511, 1023, ...];
n=3: [1, 7, 35,(155), 651, 2667, 10795, 43435, 174251, ...];
n=4: [1, 15, 155, 1395,(11811), 97155, 788035, 6347715, ...];
n=5: [1, 31, 651, 11811, 200787,(3309747), 53743987, ...];
n=6: [1, 63, 2667, 97155, 3309747, 109221651,(3548836819), ...];
n=7: [1, 127, 10795, 788035, 53743987, 3548836819, 230674393235,(14877590196755), ...]; ...
the coefficients in parenthesis give the initial terms of this sequence;
an adjacent diagonal forms the Gaussian binomial coefficients [2*n,n] for q=2:
[1, 3, 35, 1395, 200787, 109221651, 230674393235, ...] = A006098.
		

Crossrefs

Programs

  • Mathematica
    Table[QBinomial[2n-1, n, 2], {n, 0, 20}] (* Vladimir Reshetnikov, Sep 12 2016 *)
  • PARI
    {a(n)=polcoeff(prod(k=0,n-1,1/(1-2^k*x +x*O(x^n))),n)}
    for(n=0,20,print1(a(n),", "))

Formula

a(n) = [x^n] Product_{k=0..n-1} 1/(1 - 2^k*x).
a(n) ~ c * 2^(n*(n-1)), where c = A065446. - Vaclav Kotesovec, Sep 22 2016

A228465 Recurrence a(n) = a(n-1) + 2^n*a(n-2) with a(0)=0, a(1)=1.

Original entry on oeis.org

0, 1, 1, 9, 25, 313, 1913, 41977, 531705, 22023929, 566489849, 45671496441, 2366013917945, 376506912762617, 39141278944373497, 12376519796349807353, 2577539376694811306745, 1624792742123856760679161, 677311275106408471956040441, 852536648457739021814912002809
Offset: 0

Views

Author

Vaclav Kotesovec, Aug 22 2013

Keywords

Comments

Generally (if p>0, q>1), recurrence a(n) = b*a(n-1) + (p*q^n+d)*a(n-2), a(n) is asymptotic to c*q^(n^2/4)*(p*q)^(n/2), where c is for fixed parameters b, p, d, q, a(0), a(1) constant, independent on n.

Crossrefs

Programs

  • Magma
    [n le 2 select (n-1) else Self(n-1)+Self(n-2)*2^(n-1): n in [1..20]]; // Vincenzo Librandi, Aug 23 2013
    
  • Mathematica
    RecurrenceTable[{a[n]==a[n-1]+2^n*a[n-2],a[0]==0,a[1]==1},a,{n,0,20}]
    (* Alternative: *)
    a[n_] := Sum[2^(k^2-1) QBinomial[n - k , k - 1, 2], {k, 1, n}];
    Table[a[n], {n, 0, 19}] (* After Vladimir Kruchinin. Peter Luschny, Jan 20 2020 *)
  • SageMath
    def a(n):
        return sum(2^(k^2 - 1)*q_binomial(n-k , k-1, 2) for k in (1..n))
    print([a(n) for n in range(20)]) # Peter Luschny, Jan 20 2020

Formula

a(n) ~ c * 2^(n^2/4 + n/2), where c = 0.548441579870783378573455400152590154... if n is even and c = 0.800417244834941368929416800341853541... if n is odd.
a(n) = Sum_{k=1..floor(n/2+1/2)} qbinomial(n-k,k-1)*2^(k^2-1), where q-binomial is triangle A022166, that is, with q=2. - Vladimir Kruchinin, Jan 20 2020

A362903 Array read by antidiagonals: T(n,k) is the number of nonisomorphic k-tuples of involutions on a (2n)-set that pairwise commute.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 4, 3, 1, 1, 8, 11, 4, 1, 1, 16, 43, 24, 5, 1, 1, 32, 171, 176, 46, 6, 1, 1, 64, 683, 1376, 611, 80, 7, 1, 1, 128, 2731, 10944, 9281, 1864, 130, 8, 1, 1, 256, 10923, 87424, 146445, 54384, 5161, 200, 9, 1, 1, 512, 43691, 699136, 2334181, 1696352, 285939, 13184, 295, 10, 1
Offset: 0

Views

Author

Andrew Howroyd, May 11 2023

Keywords

Comments

Two involutions x,y commute if x*y = y*x. Isomorphism is up to permutation of the elements of the (2n)-set. T(n,k) also gives the values for a (2n+1)-set.

Examples

			Array begins:
======================================================
n/k| 0 1   2     3       4          5            6 ...
---+--------------------------------------------------
0  | 1 1   1     1       1          1            1 ...
1  | 1 2   4     8      16         32           64 ...
2  | 1 3  11    43     171        683         2731 ...
3  | 1 4  24   176    1376      10944        87424 ...
4  | 1 5  46   611    9281     146445      2334181 ...
5  | 1 6  80  1864   54384    1696352     53885632 ...
6  | 1 7 130  5161  285939   17562679   1110290303 ...
7  | 1 8 200 13184 1372224  165343616  20774749952 ...
8  | 1 9 295 31532 6101080 1436647664 358238974304 ...
  ...
		

Crossrefs

Columns k=0..3 are A000012, A000027(n-1), A001752, A362904.
Rows n=1..3 are A000079, A007583, A103334(n+1).

Programs

  • PARI
    \\ B(n, k) is A022166.
    B(n, k)={polcoef(x^k/prod(j=0, k, 1-2^j*x + O(x*x^n)), n)}
    C(k,n) = Vec(1/prod(j=0, min(k-1, logint(n, 2)), (1 - x^(2^j) + O(x*x^n))^B(k,j+1), 1 - x + O(x*x^n)))
    M(n,m=n) = Mat(vector(m+1, k, C(k-1, n)~))
    { my(A=M(7)); for(i=1, #A, print(A[i,])) }

Formula

G.f. of column k: 1/((1 - x)*Product_{j=0..k-1} (1 - x^(2^j))^A022166(k,j+1)).

A096657 a(n) = (2^n)*a(n-1) + (2^(n-1))*a(n-2), a(0)=1, a(1)=3.

Original entry on oeis.org

1, 3, 14, 124, 2096, 69056, 4486656, 578711552, 148724449280, 76295068188672, 78202296743231488, 160236429879963287552, 656488575092059763900416, 5378610735570941915498020864, 88128536246001466497105446043648
Offset: 0

Views

Author

Clark Kimberling, Jul 01 2004

Keywords

Comments

This is the sequence of numerators of self-convergents to the number 1.40861... whose self-continued fraction is (1,2,4,8,16,...)=A000079. See A096658 for denominators and A096654 for definitions.

Examples

			a(2)=4*3+2*1=14, a(3)=8*14+4*3=124.
		

Crossrefs

Programs

  • Mathematica
    a[0] = 1; a[1] = 3; a[n_] := (2^n)*a[n-1] + (2^(n-1))*a[n-2]; Table[ a[n], {n, 0, 14}] (* Robert G. Wilson v, Jul 03 2004 *)
    b[n_, k_] := k^2 - k (1 + n) +  n (1 + n)/2;
    a[n_] := Sum[2^b[n, k] QBinomial[n - k + 1, k, 2], {k, 0, n + 1}] ;
    Table[a[n], {n, 0, 14}] (* After Vladimir Kruchinin, Peter Luschny, Jan 19 2020 *)

Formula

a(n) is asymptotic to c*2^(n(n+1)/2) where c = 2.1726687508496636560169136... - Benoit Cloitre, Jul 02 2004
c = 1 + Sum_{k>=1} (Product_{j=1..k} 1/(2^(j-1)*(2^j-1))) = 2.172668750849663656016913609859312820656436935109608860295... . - Vaclav Kotesovec, Nov 27 2015
a(n) = Sum_{k=0..n+1} q-binomial(n-k+1,k)*2^(binomial(n-k+1,2)+binomial(k,2)), where q-binomial is triangle A022166, that is, with q=2. - Vladimir Kruchinin, Jan 19 2020

Extensions

More terms from Benoit Cloitre, Jul 02 2004

A288853 Triangle read by rows: T(n,k) is the number of surjective linear mappings from an n-dimensional vector space over F_2 onto a k-dimensional vector space, n>=0, 0<=k<=n.

Original entry on oeis.org

1, 1, 1, 1, 3, 6, 1, 7, 42, 168, 1, 15, 210, 2520, 20160, 1, 31, 930, 26040, 624960, 9999360, 1, 63, 3906, 234360, 13124160, 629959680, 20158709760, 1, 127, 16002, 1984248, 238109760, 26668293120, 2560156139520, 163849992929280, 1, 255, 64770, 16322040, 4047865920, 971487820800, 217613271859200, 41781748196966400, 5348063769211699200
Offset: 0

Views

Author

Geoffrey Critzer, Jun 18 2017

Keywords

Comments

The (q = 2) analog of A008279.
A022166(m,k)*T(n,k) is the number of m X n matrices over F_2 that have rank k.
a(n) is the number of n X n matrices over F_2 in Green's R class containing A where rank(A) = k. - Geoffrey Critzer, Oct 05 2022

Examples

			  1;
  1,  1;
  1,  3,   6;
  1,  7,  42,   168;
  1, 15, 210,  2520,  20160;
  1, 31, 930, 26040, 624960, 9999360;
  ...
		

Crossrefs

Columns k=0-10 give: A000012, A000225, 6*A006095, 168*A006096, 20160*A006097, 9999360*A006110, 20158709760*A022189, 163849992929280*A022190, 5348063769211699200*A022191, 699612310033197642547200*A022192, 366440137299948128422802227200*A022193.
Main diagonal gives A002884.
Cf. A022166.

Programs

  • Mathematica
    Table[Table[Product[q^n - q^i, {i, 0, k - 1}] /. q -> 2, {k, 0, n}], {n, 0,8}] // Grid

Formula

T(n,k) = Product_{j=0..k-1} (2^n - 2^j).
T(n,k) = A002884(k)*A022166(n,k).
Let g_m(x) = Sum_{n>=0} (2^m*x)^n/A005329(n) and e(x) = Sum_{n>=0} x^n/A005329(n). Then Sum_{k>=0} T(n,k)*x^k/A005329(k) = g_n(x)/e(x). - Geoffrey Critzer, Jun 01 2024

A305737 Number of subsets S of vectors in GF(2)^n such that span(S) = GF(2)^n.

Original entry on oeis.org

1, 2, 8, 184, 62464, 4293001088, 18446743803209556992, 340282366920938461120638132973980614656, 115792089237316195423570985008687907766497981100801256254562260326801824546816
Offset: 0

Views

Author

Geoffrey Critzer, Jun 22 2018

Keywords

Comments

Asymptotic to A001146(n) = 2^(2^n).

References

  • R. P. Stanley, Enumerative Combinatorics Vol 1, Cambridge, 1997, page 127.

Crossrefs

Programs

  • Mathematica
    Table[Sum[QBinomial[n, k, q] (-1)^(n - k) q^Binomial[n - k, 2] (2^(q^k) - 1) /. q -> 2, {k, 0, n}], {n, 0, 8}]
  • PARI
    \\ here U(n,k) is A022166(n,k).
    U(n,k)={polcoeff(x^k/prod(j=0, k, 1-2^j*x+x*O(x^n)), n)}
    a(n)={sum(k=0, n, U(n,k)*(-1)^(n-k)*2^binomial(n-k,2)*(2^(2^k)-1))} \\ Andrew Howroyd, Mar 01 2020

Formula

a(n) = Sum_{k=0..n} A022166(n,k)*(-1)^(n-k)*2^binomial(n-k,2)*(2^(2^k)-1).
Sum_{k=0..n} a(k)* A022166(n,k) = 2^(2^n) - 1. - Geoffrey Critzer, Apr 25 2024
a(n) = Sum_{k=0..n} A158474(n,k) * A051179(n-k). - Tilman Piesk, Mar 12 2025

Extensions

a(8) corrected by Andrew Howroyd, Mar 01 2020

A342186 Triangle read by rows, matrix inverse of A139382.

Original entry on oeis.org

1, -1, 1, 3, -4, 1, -21, 31, -11, 1, 315, -486, 196, -26, 1, -9765, 15381, -6562, 1002, -57, 1, 615195, -978768, 428787, -69688, 4593, -120, 1, -78129765, 124918731, -55434717, 9279163, -652999, 19833, -247, 1
Offset: 1

Views

Author

John Keith, Mar 04 2021

Keywords

Comments

This triangle appears to be the q-analog of A008275 (Stirling numbers of the first kind) for q=2. However, A333142 has a similar definition.
Row sums of unsigned triangle are A006125 with offset 1.
|T(n,k)| is the number of descent free digraphs on [n] containing exactly k source nodes. A descent in a digraph is a pair of vertices s->t such that s>t. A descent free digraph is necessarily acyclic. A source in an acyclic digraph is a node with indegree 0. - Geoffrey Critzer, Mar 05 2025

Examples

			The triangle begins:
           1;
          -1,         1;
           3,        -4,         1;
         -21,        31,       -11,       1;
         315,      -486,       196,     -26,       1;
       -9765,     15381,     -6562,    1002,     -57,     1;
      615195,   -978768,    428787,  -69688,    4593,  -120,    1;
   -78129765, 124918731, -55434717, 9279163, -652999, 19833, -247, 1;
  ...
		

Crossrefs

Cf. A008275, A139382, A333142, A333143, A006125 (row sums).
Columns of unsigned triangle: A005329, A203011, A000295, A203242.

Programs

  • Maple
    A342186 := proc(n, k) if n = 1 and k = 1 then 1 elif k > n or k < 1 then 0 else
    A342186(n-1, k-1) - (2^(n-1) - 1) * A342186(n-1, k) fi end:
    for n from 1 to 8 do seq(A342186(n, k), k = 1..n) od; # Peter Luschny, Jun 28 2022
  • Mathematica
    T[1, 1] := 1; T[n_, k_] := T[n, k] = If[k > n || k < 1, 0, T[n - 1, k - 1] - (2^(n - 1) - 1)*T[n - 1, k]]; Table[T[n, k], {n, 1, 8}, {k, 1, n}] (* after G. C. Greubel's program for A139382 *)
  • PARI
    mat(nn) = my(m = matrix(nn, nn)); for (n=1, nn, for(k=1, nn, m[n,k] = if (n==1, if (k==1, 1, 0), if (k==1, 1, (2^k-1)*m[n-1, k] + m[n-1, k-1])););); m; \\ A139382
    tabl(nn) = 1/mat(nn); \\ Michel Marcus, Mar 18 2021

Formula

T(n,k) = T(n-1,k-1) - (2^(n-1)-1) * T(n-1,k), n, k >= 1, T(1, 1) = 1, T(n, 0) = 0.
For unsigned triangle, T(n, 1) = A005329(n-1); T(n, 2) = A203011(n-1); T(n, n-1) = A000295(n+1); T(n, n-2) = A203242(n-1).
T(n,k) = Sum_{j=k..n} (-1)^(n-j)*2^binomial(n-j,2)*qBinomial(n,j,2)*binomial(j,k), where qBinomial(n,k,2) is A022166(n,k). - Fabian Pereyra, Feb 08 2024

A347485 Irregular triangle read by rows: T(n, k) is the q-multinomial coefficient defined by the k-th partition of n in Abramowitz-Stegun order, evaluated at q = 2.

Original entry on oeis.org

1, 1, 3, 1, 7, 21, 1, 15, 35, 105, 315, 1, 31, 155, 465, 1085, 3255, 9765, 1, 63, 651, 1395, 1953, 9765, 22785, 29295, 68355, 205065, 615195, 1, 127, 2667, 11811, 8001, 82677, 177165, 413385, 248031, 1240155, 2893695, 3720465, 8681085, 26043255, 78129765
Offset: 1

Views

Author

Álvar Ibeas, Sep 03 2021

Keywords

Comments

Abuse of notation: we write T(n, L) for T(n, k), where L is the k-th partition of n in A-St order.
For any permutation (e_1,...,e_r) of the parts of L, T(n, L) is the number of chains of subspaces 0 < V_1 < ··· < V_r = (F_2)^n with dimension increments (e_1,...,e_r).

Examples

			The number of subspace chains 0 < V_1 < V_2 < (F_2)^3 is 21 = T(3, (1, 1, 1)). There are 7 = A022166(3, 1) choices for a one-dimensional subspace V_1 and, for each of them, 3 = A022166(2, 1) extensions to a two-dimensional subspace V_2.
Triangle begins:
  k:  1  2   3   4    5    6    7
      ---------------------------
n=1:  1
n=2:  1  3
n=3:  1  7  21
n=4:  1 15  35 105  315
n=5:  1 31 155 465 1085 3255 9765
		

References

  • R. P. Stanley, Enumerative Combinatorics (vol. 1), Cambridge University Press (1997), Section 1.3.

Crossrefs

Cf. A036038 (q = 1), A022166, A005329 (last entry in each row).

Formula

T(n, (n)) = 1. T(n, L) = A022166(n, e) * T(n - e, L \ {e}), if L is a partition of n and e < n is a part of L.
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