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 51-60 of 79 results. Next

A288267 Triangle read by rows: T(n,k) = T(n,k+1) + T(n-k,k-1) with T(0,0) = 1 and T(n,k) = 0 if k<0 or k > A003056(n).

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 2, 1, 3, 3, 1, 5, 5, 2, 9, 9, 4, 1, 15, 15, 6, 1, 26, 26, 11, 2, 45, 45, 19, 4, 78, 78, 33, 7, 1, 135, 135, 57, 12, 1, 234, 234, 99, 21, 2, 406, 406, 172, 37, 4, 704, 704, 298, 64, 7, 1222, 1222, 518, 112, 13, 1, 2120, 2120, 898, 194, 22, 1, 3679
Offset: 0

Views

Author

Seiichi Manyama, Sep 01 2017

Keywords

Examples

			First few rows are:
   1;
   1,  1;
   1,  1;
   2,  2, 1;
   3,  3, 1;
   5,  5, 2;
   9,  9, 4, 1;
  15, 15, 6, 1.
		

Crossrefs

Columns 0+1,2 give A005169, A289080 (for n>0).
Cf. A003056.

Programs

  • Maple
    T:= proc(n,k) option remember; `if`(k<0 or k*(k+1)/2>n, 0,
          `if`(n=0, 1, T(n, k+1)+T(n-k, k-1)))
        end:
    seq(seq(T(n, k), k=0..floor((sqrt(1+8*n)-1)/2)), n=0..20); # Alois P. Heinz, Sep 01 2017
  • Mathematica
    T[n_, k_] := T[n, k] = If[k < 0 || k(k+1)/2 > n, 0, If[n == 0, 1, T[n, k+1] + T[n-k, k-1]]];
    Table[T[n, k], {n, 0, 20}, {k, 0, Floor[(Sqrt[8n+1]-1)/2]}] // Flatten (* Jean-François Alcover, Nov 14 2020, after Alois P. Heinz *)

A290771 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of the continued fraction 1/(1 - x/(1 - x^(2^k)/(1 - x^(3^k)/(1 - x^(4^k)/(1 - x^(5^k)/(1 - ...)))))).

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 1, 5, 1, 1, 1, 2, 14, 1, 1, 1, 1, 3, 42, 1, 1, 1, 1, 1, 5, 132, 1, 1, 1, 1, 1, 2, 9, 429, 1, 1, 1, 1, 1, 1, 3, 15, 1430, 1, 1, 1, 1, 1, 1, 1, 4, 26, 4862, 1, 1, 1, 1, 1, 1, 1, 1, 5, 45, 16796, 1, 1, 1, 1, 1, 1, 1, 1, 1, 7, 78, 58786, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 10, 135, 208012
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 10 2017

Keywords

Examples

			Square array begins:
   1,  1,  1,  1,  1,  1, ...
   1,  1,  1,  1,  1,  1, ...
   2,  1,  1,  1,  1,  1, ...
   5,  2,  1,  1,  1,  1, ...
  14,  3,  1,  1,  1,  1, ...
  42,  5,  2,  1,  1,  1, ...
		

Crossrefs

Columns k = 0..5 give A000108, A005169, A206739, A291146, A291149, A291168.

Programs

  • Mathematica
    Table[Function[k, SeriesCoefficient[1/(1 + ContinuedFractionK[-x^(i^k), 1, {i, 1, n}]), {x, 0, n}]][j - n], {j, 0, 12}, {n, 0, j}] // Flatten

Formula

G.f. of column k: 1/(1 - x/(1 - x^(2^k)/(1 - x^(3^k)/(1 - x^(4^k)/(1 - x^(5^k)/(1 - ...)))))), a continued fraction.

A291652 Square array A(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of k-th power of continued fraction 1/(1 - x/(1 - x^2/(1 - x^3/(1 - x^4/(1 - x^5/(1 - ...)))))).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 1, 0, 1, 3, 3, 2, 0, 1, 4, 6, 6, 3, 0, 1, 5, 10, 13, 11, 5, 0, 1, 6, 15, 24, 27, 20, 9, 0, 1, 7, 21, 40, 55, 54, 38, 15, 0, 1, 8, 28, 62, 100, 120, 109, 70, 26, 0, 1, 9, 36, 91, 168, 236, 258, 216, 129, 45, 0, 1, 10, 45, 128, 266, 426, 540, 544, 423, 238, 78, 0, 1, 11, 55, 174, 402, 721, 1035, 1205, 1127, 824, 437, 135, 0
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 28 2017

Keywords

Examples

			G.f. of column k: A_k(x) = 1 + k*x + k*(k + 1)*x^2/2 +  k*(k^2 + 3*k + 8)*x^3/6 + k*(k^3 + 6*k^2 + 35*k + 30)*x^4/24 + ...
Square array begins:
1,  1,   1,   1,    1,    1,  ...
0,  1,   2,   3,    4,    5,  ...
0,  1,   3,   6,   10,   15,  ...
0,  2,   6,  13,   24,   40,  ...
0,  3,  11,  27,   55,  100,  ...
0,  5,  20,  54,  120,  236,  ...
		

Crossrefs

Columns k=0..1 give A000007, A005169.
Rows n=0..3 give A000012, A001477, A000217, A003600 (with a(0)=0).
Main diagonal gives A291653.

Programs

  • Mathematica
    Table[Function[k, SeriesCoefficient[1/(1 + ContinuedFractionK[-x^i, 1, {i, 1, n}])^k, {x, 0, n}]][j - n], {j, 0, 12}, {n, 0, j}] // Flatten
    Table[Function[k, SeriesCoefficient[((Sum[(-1)^i x^(i (i + 1))/Product[(1 - x^m), {m, 1, i}], {i, 0, n}])/(Sum[(-1)^i x^(i^2)/Product[(1 - x^m), {m, 1, i}], {i, 0, n}]))^k, {x, 0, n}]][j - n], {j, 0, 12}, {n, 0, j}] // Flatten

Formula

G.f. of column k: (1/(1 - x/(1 - x^2/(1 - x^3/(1 - x^4/(1 - x^5/(1 - ...)))))))^k, a continued fraction.

A301627 G.f. A(x) satisfies: A(x) = 1/(1 - x*A(x)/(1 - x^2*A(x)^2/(1 - x^3*A(x)^3/(1 - x^4*A(x)^4/(1 - ...))))), a continued fraction.

Original entry on oeis.org

1, 1, 2, 6, 20, 71, 265, 1024, 4059, 16414, 67451, 280856, 1182379, 5024361, 21522055, 92833874, 402879747, 1757852317, 7706728006, 33932931008, 149986338830, 665276977574, 2960306454110, 13210976195068, 59114318997648, 265166069469324, 1192145264317628, 5370983954821322
Offset: 0

Views

Author

Ilya Gutkovskiy, Mar 24 2018

Keywords

Examples

			G.f. A(x) = 1 + x + 2*x^2 + 6*x^3 + 20*x^4 + 71*x^5 + 265*x^6 + 1024*x^7 + 4059*x^8 + 16414*x^9 + 67451*x^10 + ...
log(A(x)) = x + 3*x^2/2 + 13*x^3/3 + 55*x^4/4 + 236*x^5/5 + 1035*x^6/6 + 4593*x^7/7 + 20551*x^8/8 + ... + A291653(n)*x^n/n + ...
		

Crossrefs

Formula

a(n) ~ c * d^n / n^(3/2), where d = 4.760595370947474723688065553003203505424287110594102605580439495640678... and c = 0.395762805862214496152624315213041270339036... - Vaclav Kotesovec, Apr 08 2018

A301921 Expansion of e.g.f. 1/(1 - (exp(x) - 1)/(1 - (exp(x) - 1)^2/(1 - (exp(x) - 1)^3/(1 - ...)))), a continued fraction.

Original entry on oeis.org

1, 1, 3, 19, 159, 1651, 21303, 324619, 5653119, 110909251, 2424648903, 58430418619, 1537673312079, 43860906193651, 1347852526593303, 44392923532503019, 1560023977386027039, 58259266750803410851, 2303999137417453606503, 96188099015599819297819, 4227325636692027926037999
Offset: 0

Views

Author

Ilya Gutkovskiy, Jun 19 2018

Keywords

Comments

From Peter Bala, Aug 19 2025: (Start)
Conjecture: Let k be a positive integer. The sequence obtained by reducing a(n) modulo k is eventually periodic with the period dividing phi(k) = A000010(k). For example, modulo 9 we obtain the sequence [0, 1, 3, 1, 6, 4, 0, 7, 3, 1, 6, 4, 0, 7, 3, 1, 6, 4, 0, 7, ...] with an apparent period of 6 = phi(9) beginning at n = 2. Cf. A004123. (End)

Examples

			E.g.f.: A(x) = 1 + x + 3*x^2/2! + 19*x^3/3! + 159*x^4/4! + 1651*x^5/5! + 21303*x^6/6! + ...
		

Crossrefs

Programs

  • Mathematica
    nmax = 20; CoefficientList[Series[1/(1 + ContinuedFractionK[-(Exp[x] - 1)^k, 1, {k, 1, nmax}]), {x, 0, nmax}], x] Range[0, nmax]!
    b[n_] := b[n] = SeriesCoefficient[1/(1 + ContinuedFractionK[-x^k, 1, {k, 1, n}]), {x, 0, n}]; a[n_] := a[n] = Sum[StirlingS2[n, k] b[k] k!, {k, 0, n}]; Table[a[n], {n, 0, 20}]

Formula

a(n) = Sum_{k=0..n} Stirling2(n,k)*A005169(k)*k!.
a(n) ~ c * d^n * n!, where d = 2.19787763261059933075080498218168228... and c = 0.250957960982243982921501085974065... - Vaclav Kotesovec, Dec 20 2018

A058300 Number of ways of piling up n wine bottles above a row of n+1 bottles at ground level.

Original entry on oeis.org

1, 1, 1, 3, 7, 16, 43, 115, 303, 813, 2203, 5991, 16371, 44917, 123598, 340988, 942930, 2612735, 7252407, 20163046, 56136326, 156488946, 436739752, 1220157514, 3412116339, 9550192161, 26751643663, 74991516850, 210364915858, 590490257667, 1658484275955
Offset: 0

Views

Author

Roland Bacher, Dec 08 2000

Keywords

Comments

Related to the Catalan numbers (which count the ways of storing an arbitrary number of bottles above n bottles at ground level).
Related to fountains of n coins (A005169). [Joerg Arndt, Mar 18 2011]

Examples

			a(4) = 7: the seven possibilities are:
..............0.............0.........0...............0.........0............0
.0.0.0.0.....0.0.0.......0.0.0.......0.0...0.....0...0.0.......0.0.0......0.0.0
0.0.0.0.0.,.0.0.0.0.0.,.0.0.0.0.0.,.0.0.0.0.0.,.0.0.0.0.0.,.0.0.0.0.0,.0.0.0.0.0
		

References

  • R. P. Stanley, Enumerative Combinatorics (Volume 2); see Exercise 6.19(hhh).

Crossrefs

Cf. A047998.

Programs

  • Mathematica
    terms = 31; initialMax = 5; Clear[g]; g[max_] := g[max] = (Print["max = ", max]; f = 1/Fold[1 - y*x^#2/#1&, 1, Range[max] // Reverse]; b[n_, k_] := SeriesCoefficient[f, {x, 0, n}, {y, 0, k}]; b[0, 0] = 1; Clear[a]; a[n_] := a[n] = b[2n+1, n+1]; Array[a, terms, 0]); g[max = initialMax]; g[max = max+1]; While[g[max] != g[max-1], max = max+1]; A058300 = g[max] (* Jean-François Alcover, Oct 05 2017, after Alois P. Heinz's formula *)

Formula

Coefficient of w^(2*n+1)*z^(n+1) in the formal power series G(w, z) defined by G(w, z)=1+w*z*G(w, w*z).
a(n) = A047998(2n+1,n+1). - Alois P. Heinz, Jun 24 2015
a(n) ~ c * d^n / sqrt(n), where d = 2.8566122635122125634030051... and c = 0.19212135026441477122126... - Vaclav Kotesovec, Jul 17 2019

Extensions

More terms from Alois P. Heinz, Jun 24 2015

A167751 Diagonal sums of A167749.

Original entry on oeis.org

1, 0, 1, 1, 2, 4, 7, 14, 27, 52, 102, 198, 387, 755, 1474, 2879, 5622, 10982, 21450, 41900, 81847, 159880, 312315, 610086, 1191768, 2328054, 4547732, 8883767, 17354001, 33900200, 66222412, 129362318, 252703135, 493643580, 964309346
Offset: 0

Views

Author

Paul Barry, Nov 10 2009

Keywords

Comments

Hankel transform is A167753.

Examples

			G.f. = 1 + x^2 + x^3 + 2*x^4 + 4*x^5 + 7*x^6 + 14*x^7 + 27*x^8 + 52*x^9 + ...
		

Formula

G.f.: 1/(1-x^2/(1-x/(1-x^2/(1-x^3/(1-x^4/(1-...)))))) (continued fraction);
G.f.: 1/(1-x^2*f(x)), f(x) the g.f. of A005169.

A168445 Number of compositions a(1),...,a(k) of n, for some k, such that a(i+1) <= a(i) + 1 for 1 <= i < k and a(1) <= a(k) + 1.

Original entry on oeis.org

1, 2, 4, 6, 11, 18, 31, 52, 91, 155, 268, 464, 802, 1390, 2411, 4178, 7249, 12578, 21823, 37870, 65724, 114061, 197960, 343578, 596317, 1034983, 1796359, 3117837, 5411478, 9392460, 16302081, 28294850, 49110242, 85238716, 147945552, 256783448, 445689300
Offset: 1

Views

Author

Vladeta Jovovic, Nov 25 2009

Keywords

References

  • Steven R. Finch, Mathematical Constants, Cambridge, 2003, p. 381.

Crossrefs

Programs

  • Maple
    b:= proc(n,r,f) option remember; `if`(n=0, `if`(f-1<=r, 1, 0),
          add(b(n-i, i, f), i=1..min(r+1, n)))
        end:
    a:= n-> add(b(n-i, i, i), i=1..n):
    seq(a(n), n=1..40);  # Alois P. Heinz, Dec 15 2009
  • Mathematica
    b[n_, r_, f_] := b[n, r, f] = If[n == 0, If[f - 1 <= r, 1, 0], Sum[b[n - i, i, f], {i, 1, Min [r + 1, n]}]];
    a[n_] := Sum[b[n - i, i, i], {i, 1, n}];
    Array[a, 40] (* Jean-François Alcover, Nov 10 2020, after Alois P. Heinz *)

Formula

a(n) ~ c / r^n, where r = A347901 = 0.576148769142756602297868573719938782354724663118974... is the lowest root of the equation Sum_{k>=0} (-1)^k * r^(k^2) / QPochhammer(r, r, k) = 0 and c = 0.6149126319329581124890112676009720339906790088212712130894... - Vaclav Kotesovec, May 01 2014, updated Sep 09 2020

Extensions

More terms from Alois P. Heinz, Dec 15 2009

A187080 Triangle T(n,k) read by rows: fountains of n coins and height k.

Original entry on oeis.org

1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 2, 0, 0, 0, 1, 4, 0, 0, 0, 0, 1, 7, 1, 0, 0, 0, 0, 1, 12, 2, 0, 0, 0, 0, 0, 1, 20, 5, 0, 0, 0, 0, 0, 0, 1, 33, 11, 0, 0, 0, 0, 0, 0, 0, 1, 54, 22, 1, 0, 0, 0, 0, 0, 0, 0, 1, 88, 44, 2, 0, 0, 0, 0, 0, 0, 0, 0, 1, 143, 85, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 232, 161, 12, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 376, 302, 25, 0, 0, 0
Offset: 0

Views

Author

Joerg Arndt, Mar 08 2011

Keywords

Comments

See A005169 for the definition of a "fountain of n coins". [John W. Layman, Mar 10 2011]

Examples

			Triangle begins:
1;
0,1;
0,1,0;
0,1,1,0;
0,1,2,0,0;
0,1,4,0,0,0;
0,1,7,1,0,0,0;
0,1,12,2,0,0,0,0;
0,1,20,5,0,0,0,0,0;
0,1,33,11,0,0,0,0,0,0;
0,1,54,22,1,0,0,0,0,0,0;
0,1,88,44,2,0,0,0,0,0,0,0;
0,1,143,85,5,0,0,0,0,0,0,0,0;
0,1,232,161,12,0,0,0,0,0,0,0,0,0;
0,1,376,302,25,0,0,0,0,0,0,0,0,0,0;
0,1,609,559,52,1,0,0,0,0,0,0,0,0,0,0;
0,1,986,1026,105,2,0,0,0,0,0,0,0,0,0,0,0;
0,1,1596,1870,207,5,0,0,0,0,0,0,0,0,0,0,0,0;
The 15 compositions corresponding to fountains of 7 coins are the following:
   #:    composition      height
   1:    [ 1 2 3 1 ]        3
   2:    [ 1 2 2 2 ]        2
   3:    [ 1 1 2 3 ]        3
   4:    [ 1 2 2 1 1 ]      2
   5:    [ 1 2 1 2 1 ]      2
   6:    [ 1 1 2 2 1 ]      2
   7:    [ 1 2 1 1 2 ]      2
   8:    [ 1 1 2 1 2 ]      2
   9:    [ 1 1 1 2 2 ]      2
  10:    [ 1 2 1 1 1 1 ]    2
  11:    [ 1 1 2 1 1 1 ]    2
  12:    [ 1 1 1 2 1 1 ]    2
  13:    [ 1 1 1 1 2 1 ]    2
  14:    [ 1 1 1 1 1 2 ]    2
  15:    [ 1 1 1 1 1 1 1 ]  1
  stats:  0 1 12 2 0 0 0 0
		

Crossrefs

Row sums give A005169 (fountains of n coins).
Cf. A047998, A187081 (sandpiles by height).

Programs

  • Mathematica
    b[n_, i_, h_] := b[n, i, h] = If[n == 0, x^h, Sum[b[n - j, j, Max[h, j]], {j, 1, Min[i + 1, n]}]];
    T[n_] := Table[Coefficient[#, x, i], {i, 0, n}]& @ b[n, 0, 0];
    Table[T[n], {n, 0, 25}] // Flatten (* Jean-François Alcover, May 31 2019, after Alois P. Heinz in A291878 *)

Formula

T(n,1) + T(n,2) = Fibonacci(n).

A206737 G.f.: 1/(1 - x/(1 - x^4/(1 - x^7/(1 - x^10/(1 - x^13/(1 - x^16/(1 -...- x^(3*n-2)/(1 -...)))))))), a continued fraction.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 3, 4, 5, 7, 10, 14, 20, 28, 39, 54, 76, 107, 150, 210, 294, 412, 578, 811, 1137, 1593, 2233, 3131, 4390, 6155, 8629, 12097, 16959, 23777, 33336, 46737, 65524, 91863, 128790, 180563, 253149, 354912, 497581, 697602, 978031, 1371190, 1922395
Offset: 0

Views

Author

Paul D. Hanna, Feb 12 2012

Keywords

Comments

We have the simple continued fraction expansions (A(x) is the sequence o.g.f.): A(1/n) = [1; n - 2, 1, n^3 - 2, 1, n^4 - 2, 1, n^6 - 2, 1, n^7 - 2, 1, n^9 - 2, 1, n^10 - 2, 1, ...] for n >= 3 and A(-1/n) = [0; 1, n - 1, 1, n^3 - 1, n^4 - 1, 1, n^6 - 1, n^7 - 1, 1, n^9 - 1, n^10 - 1, 1, ...] for n >= 2. Cf. A005169, A111317 and A143951. - Peter Bala, Dec 15 2015

Examples

			G.f.: A(x) = 1 + x + x^2 + x^3 + x^4 + 2*x^5 + 3*x^6 + 4*x^7 + 5*x^8 + ...
Simple continued fraction expansions: A(1/10) = 1.11112345816325284441923227158 ... = [1, 8, 1, 998, 1, 9998, 1, 999998, 1, 9999998, 1, 999999998, 1, 9999999998, 1, ...]; A(-1/10) = 0.909082643877542661578687284018 ... = [0, 1, 9, 1, 999, 9999, 1, 999999, 9999999, 1, 999999999, 9999999999, 1, ...]. - _Peter Bala_, Dec 15 2015
		

Crossrefs

Programs

  • Maple
    N:= 100: # to get a(0) .. a(N)
    C:= [0,[1,1],seq([-x^i,1],i=1..N,3)]:
    S:= series(numtheory:-cfrac(C),x,N+1):
    seq(coeff(S,x,j),j=0..N); # Robert Israel, Dec 28 2015
  • Mathematica
    max = 15; CF = 1+x*O[x]^max; M = Sqrt[max+1]//Floor; For[k=0, k <= M, k++, CF = 1/(1-x^(3M-3k+1)*CF)]; CoefficientList[CF, x] (* Jean-François Alcover, Dec 29 2015, adapted from PARI *)
    nmax = 50; CoefficientList[Series[1/Fold[(1 - #2/#1) &, 1, Reverse[x^(3*Range[nmax + 1]-2)]], {x, 0, nmax}], x] (* Vaclav Kotesovec, Aug 25 2017 *)
  • PARI
    {a(n)=local(CF=1+x*O(x^n),M=sqrtint(n+1)); for(k=0, M, CF=1/(1-x^(3*M-3*k+1)*CF)); polcoeff(CF, n, x)}
    for(n=0,55,print1(a(n),", "))

Formula

a(n) ~ c * d^n, where d = 1.40198938377739909105003523518827... and c = 0.34165269320144328278000954698... - Vaclav Kotesovec, Aug 25 2017
From Peter Bala, Jul 03 2019: (Start)
O.g.f. as a ratio of q-series: N(q)/D(q), where N(q) = Sum_{n >= 0} (-1)^n*q^(3*n^2+n)/((1-q^3)*(1-q^6)*...*(1-q^(3*n))) and D(q) = Sum_{n >= 0} (-1)^n*q^(3*n^2-2*n)/((1-q^3)*(1-q^6)*...*(1-q^(3*n))). Cf. A143951, A224704 and A206738.
D(q) has a simple real zero at x = 0.7132721628.... The constants c and d quoted in the above asymptotic approximation for a(n) are given by d = 1/x and c = - N(x)/(x*D'(x)), where the prime indicates differentiation w.r.t. q. (End)
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