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 1-10 of 22 results. Next

A294467 Binomial transform of A088311.

Original entry on oeis.org

1, 2, 5, 22, 113, 746, 6037, 55070, 548417, 6281938, 79935941, 1087584422, 16109401585, 255667890362, 4358283982613, 79893373511086, 1542859916102657, 31322024816838050, 676027617881188357, 15287136167625123638, 362322855217463741681
Offset: 0

Views

Author

Vaclav Kotesovec, Oct 31 2017

Keywords

Crossrefs

Programs

  • Magma
    m:=30; R:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!(Exp(x)*(&*[1 + x^k: k in [1..50]]))); [Factorial(n-1)*b[n]: n in [1..m]]; // G. C. Greubel, Oct 15 2018
  • Mathematica
    Table[Sum[Binomial[n, k]*k!*PartitionsQ[k], {k, 0, n}], {n, 0, 20}]
  • PARI
    x='x+O('x^30); Vec(serlaplace(exp(x)*eta(x^2)/eta(x))) \\ G. C. Greubel, Oct 15 2018
    

Formula

a(n) ~ exp(1) * n! * A000009(n).
a(n) ~ sqrt(2*Pi) * exp(Pi*sqrt(n/3) - n + 1) * n^(n - 1/4) / (4*3^(1/4)).
E.g.f.: exp(x) * Product_{k>=1} (1 + x^k). - Ilya Gutkovskiy, Oct 15 2018

A294468 Inverse binomial transform of A088311.

Original entry on oeis.org

1, 0, 1, 8, 9, 224, 1225, 11304, 103537, 1431296, 15642801, 206721800, 3295533241, 47467875168, 859354139449, 15596241280424, 283240963555425, 5859309797252864, 129874369387025377, 2752905169704533256, 67640333903657850601
Offset: 0

Views

Author

Vaclav Kotesovec, Oct 31 2017

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Sum[(-1)^(n-k)*Binomial[n, k]*k!*PartitionsQ[k], {k, 0, n}], {n, 0, 20}]
    max = 20; t = Table[k!*PartitionsQ[k], {k, 0, max}]; Table[Differences[t, n], {n, 0, max}][[All, 1]] (* Jean-François Alcover, Nov 02 2017 *)

Formula

a(n) = Sum_{k=0..n} (-1)^(n-k) * binomial(n,k) * A088311(k).
a(n) ~ exp(-1) * n! * A000009(n).
a(n) ~ sqrt(2*Pi) * exp(Pi*sqrt(n/3) - n - 1) * n^(n - 1/4) / (4*3^(1/4)).
E.g.f.: exp(-x) * Product_{k>=1} (1 + x^k). - Ilya Gutkovskiy, Oct 15 2018

A351884 Irregular triangle read by rows: T(n,k) is the number of sets of lists with distinct block sizes (as in A088311(n)) and containing exactly k lists.

Original entry on oeis.org

1, 0, 1, 0, 2, 0, 6, 6, 0, 24, 24, 0, 120, 240, 0, 720, 1440, 720, 0, 5040, 15120, 5040, 0, 40320, 120960, 80640, 0, 362880, 1451520, 1088640, 0, 3628800, 14515200, 14515200, 3628800, 0, 39916800, 199584000, 199584000, 39916800, 0, 479001600, 2395008000, 3353011200, 958003200
Offset: 0

Views

Author

Geoffrey Critzer, Feb 23 2022

Keywords

Examples

			Triangle T(n,k) begins:
  1;
  0,     1;
  0,     2;
  0,     6,      6;
  0,    24,     24;
  0,   120,    240;
  0,   720,   1440,   720;
  0,  5040,  15120,  5040;
  0, 40320, 120960, 80640;
  ...
		

Crossrefs

Columns k=0-1 give: A000007, A000142 (for n>=1).
Cf. A088311 (row sums).
T(A000217(n),n) gives A052295.

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
          b(n, i-1)+expand(x*b(n-i, min(i-1, n-i)))*n!/(n-i)!))
        end:
    T:= n-> (p-> seq(coeff(p, x, i), i=0..degree(p)))(b(n$2)):
    seq(T(n), n=0..12);  # Alois P. Heinz, Feb 23 2022
  • Mathematica
    nn = 13; Prepend[Map[Prepend[#, 0] &, Drop[Map[Select[#, # > 0 &] &,Range[0, nn]! CoefficientList[Series[Product[1 + y x^i, {i, 1, nn}], {x, 0, nn}],{x,y}]], 1]], {1}] // Grid

Formula

E.g.f.: Product_{i>=1} (1 + y*x^i).
Sum_{k=0..A003056(n)} (-1)^k * T(n,k) = A293140(n). - Alois P. Heinz, Feb 23 2022

A305550 Expansion of e.g.f. Product_{k>=1} (1 + (exp(x) - 1)^k).

Original entry on oeis.org

1, 1, 3, 19, 135, 1171, 12543, 156619, 2185095, 33787171, 579341583, 10927420219, 223956672855, 4940901389971, 116678668726623, 2938719256363819, 78709685812037415, 2234633592020685571, 67005923560416063663, 2114549937496479803419, 70024572874029038582775, 2427790107567416812409971
Offset: 0

Views

Author

Ilya Gutkovskiy, Jun 15 2018

Keywords

Comments

Stirling transform of A088311.
From Peter Bala, Jul 08 2022: (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 16 we obtain the sequence [1, 1, 3, 3, 7, 3, 15, 11, 7, 3, 15, 11, 7, 3, 15, 11, ...], with an apparent period of 4 beginning at a(4). Cf. A167137.
More generally, we conjecture that the same property holds for integer sequences having an e.g.f. of the form G(exp(x) - 1), where G(x) is an integral power series. (End)

Crossrefs

Programs

  • Maple
    b:= proc(n) option remember; `if`(n=0, 1, add(b(n-j)*add(
         `if`(d::odd, d, 0), d=numtheory[divisors](j)), j=1..n)/n)
        end:
    a:= n-> add(Stirling2(n, k)*k!*b(k), k=0..n):
    seq(a(n), n=0..25);  # Alois P. Heinz, Jun 15 2018
  • Mathematica
    nmax = 21; CoefficientList[Series[Product[(1 + (Exp[x] - 1)^k), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
    nmax = 21; CoefficientList[Series[Exp[Sum[(-1)^k (Exp[x] - 1)^k/(k ((Exp[x] - 1)^k - 1)), {k, 1, nmax}]], {x, 0, nmax}], x] Range[0, nmax]!
    Table[Sum[StirlingS2[n, k] PartitionsQ[k] k!, {k, 0, n}], {n, 0, 21}]

Formula

E.g.f.: exp(Sum_{k>=1} (-1)^k*(exp(x) - 1)^k/(k*((exp(x) - 1)^k - 1))).
a(n) = Sum_{k=0..n} Stirling2(n,k)*A088311(k).
From Vaclav Kotesovec, Jun 17 2018: (Start)
a(n) ~ n! * exp(Pi*sqrt(n/(6*log(2))) + (1/log(2) - 1) * Pi^2/48) / (2^(9/4) * 3^(1/4) * n^(3/4) * (log(2))^(n + 1/4)).
a(n) ~ sqrt(Pi) * exp(Pi*sqrt(n/(6*log(2))) + (1/log(2) - 1) * Pi^2/48 - n) * n^(n + 1/2) / (2^(7/4) * 3^(1/4) * n^(3/4) * (log(2))^(n + 1/4)).
(End)

A293135 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of e.g.f. Product_{i>0} Sum_{j=0..k} x^(j*i)/j!.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 1, 2, 0, 1, 1, 3, 12, 0, 1, 1, 3, 12, 48, 0, 1, 1, 3, 13, 72, 360, 0, 1, 1, 3, 13, 72, 480, 2880, 0, 1, 1, 3, 13, 73, 500, 3780, 25200, 0, 1, 1, 3, 13, 73, 500, 4020, 35280, 241920, 0, 1, 1, 3, 13, 73, 501, 4050, 37380, 372960, 2903040, 0
Offset: 0

Views

Author

Seiichi Manyama, Oct 01 2017

Keywords

Examples

			Square array begins:
   1,   1,   1,   1,   1, ...
   0,   1,   1,   1,   1, ...
   0,   2,   3,   3,   3, ...
   0,  12,  12,  13,  13, ...
   0,  48,  72,  72,  73, ...
   0, 360, 480, 500, 500, ...
		

Crossrefs

Columns k=0..5 give A000007, A088311, A293138, A293195, A293196, A293197.
Rows n=0 gives A000012.
Main diagonal gives A000262.
Cf. A293139.

Programs

  • Maple
    b:= proc(n, i, k) option remember; `if`(n=0, 1, `if`(i<1, 0,
          add(b(n-i*j, i-1, k)/j!, j=0..min(k, n/i))))
        end:
    A:= (n, k)-> n!*b(n$2, k):
    seq(seq(A(n, d-n), n=0..d), d=0..12);  # Alois P. Heinz, Oct 02 2017
  • Mathematica
    b[n_, i_, k_] := b[n, i, k] = If[n == 0, 1, If[i < 1, 0, Sum[b[n - i j, i - 1, k]/j!, {j, 0, Min[k, n/i]}]]];
    A[n_, k_] := n! b[n, n, k];
    Table[Table[A[n, d - n], {n, 0, d}], {d, 0, 12}] // Flatten (* Jean-François Alcover, Dec 06 2019, after Alois P. Heinz *)

A239841 Ordered pairs of permutation functions on n elements where f(g(g(x))) = g(g(f(x))).

Original entry on oeis.org

1, 1, 4, 30, 312, 3720, 64080, 1305360, 33949440, 1019692800, 36360576000, 1487539468800, 69633899596800, 3649476307276800, 213929162589542400, 13848506938506240000, 986705192227442688000, 76724136092268048384000, 6491471142159880740864000
Offset: 0

Views

Author

Chad Brewbaker, Mar 27 2014

Keywords

Comments

From Paul Boddington, Feb 24 2015: (Start)
Suppose G is the symmetric group on n letters. For each g in G, the set of f satisfying fgg = ggf is just the centralizer Z_gg(G). However |Z_gg(G)| is clearly constant on conjugacy classes of G. By the orbit-stabilizer theorem the size of the conjugacy class containing g is |G| / |Z_g(G)|. Since |G| = n! and Z_g(G) is a subgroup of Z_gg(G) we see that a(n) equals n! multiplied by the sum of indices |Z_gg(G) : Z_g(G)| where the sum is over representatives of the conjugacy classes of G. Since the conjugacy classes of G correspond to partitions of n (A000041), this makes it relatively easy to find terms.
a(n) appears to equal n! * A082733(n).
(End)

References

  • John F. Humphreys, A Course In Group Theory, Oxford Science Publications, 1996, chapter 10.

Crossrefs

Extensions

a(8)-a(9) from Giovanni Resta, Mar 27 2014
More terms from Paul Boddington, Feb 23 2015

A239836 Number of ordered pairs of permutation functions f,g on a size n set where f(g(g(x))) = g(f(f(x))).

Original entry on oeis.org

1, 1, 2, 6, 48, 360, 2880, 20160, 241920, 3265920, 47174400, 678585600, 12933043200, 193037644800, 3661488230400, 74537438976000, 1736591560704000, 36991492521984000
Offset: 0

Views

Author

Chad Brewbaker, Mar 27 2014

Keywords

Crossrefs

Formula

a(n) = A255525(n) * n!.

Extensions

a(8)-a(9) from Giovanni Resta, Mar 27 2014
a(10)-a(16) from Max Alekseyev, Jan 29 2025

A320350 Expansion of e.g.f. Product_{k>=1} (1 + log(1/(1 - x))^k).

Original entry on oeis.org

1, 1, 3, 20, 148, 1384, 15728, 207696, 3094152, 51423288, 945943512, 19083180192, 418550811600, 9907493349168, 251588827187280, 6820899616891008, 196645361557479552, 6007407711127690752, 193842462200078260224, 6586904673329133618432, 235079477736802622742528, 8790132360155070084076800
Offset: 0

Views

Author

Ilya Gutkovskiy, Oct 11 2018

Keywords

Crossrefs

Programs

  • Maple
    seq(n!*coeff(series(mul((1 + log(1/(1 - x))^k),k=1..100),x=0,22),x,n),n=0..21); # Paolo P. Lava, Jan 09 2019
  • Mathematica
    nmax = 21; CoefficientList[Series[Product[(1 + Log[1/(1 - x)]^k), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
    Table[Sum[Abs[StirlingS1[n, k]] PartitionsQ[k] k!, {k, 0, n}], {n, 0, 21}]

Formula

a(n) = Sum_{k=0..n} |Stirling1(n,k)|*A000009(k)*k!.
From Vaclav Kotesovec, Oct 13 2018: (Start)
a(n) ~ n! * exp(n + Pi*sqrt(n/(3*(exp(1) - 1))) + Pi^2/(24*(exp(1) - 1))) / (4 * 3^(1/4) * n^(3/4) * (exp(1) - 1)^(n + 1/4)).
a(n) ~ sqrt(Pi) * exp(Pi*sqrt(n/(3*(exp(1) - 1))) + Pi^2/(24*(exp(1) - 1))) * n^(n - 1/4) / (2^(3/2) * 3^(1/4) * (exp(1) - 1)^(n + 1/4)).
(End)

A298905 Expansion of e.g.f. Product_{k>=1} (1 + log(1 + x)^k).

Original entry on oeis.org

1, 1, 1, 8, -8, 224, -712, 9120, -53496, 980088, -14394648, 264140832, -4113747024, 59028225840, -545558201424, -4191307074432, 450100910950272, -17302659472138752, 530508727766191104, -14790496500550616832, 408513443917280375808, -12274212131738107257600
Offset: 0

Views

Author

Ilya Gutkovskiy, Jun 18 2018

Keywords

Crossrefs

Programs

  • Maple
    b:= proc(n) option remember; `if`(n=0, 1, add(b(n-j)*add(
         `if`(d::odd, d, 0), d=numtheory[divisors](j)), j=1..n)/n)
        end:
    a:= n-> add(Stirling1(n, j)*b(j)*j!, j=0..n):
    seq(a(n), n=0..23);  # Alois P. Heinz, Jun 18 2018
  • Mathematica
    nmax = 21; CoefficientList[Series[Product[(1 + Log[1 + x]^k), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
    nmax = 21; CoefficientList[Series[Exp[Sum[(-1)^(k + 1) Log[1 + x]^k/(k (1 - Log[1 + x]^k)), {k, 1, nmax}]], {x, 0, nmax}], x] Range[0, nmax]!
    Table[Sum[StirlingS1[n, k] PartitionsQ[k] k!, {k, 0, n}], {n, 0, 21}]

Formula

E.g.f.: exp(Sum_{k>=1} (-1)^(k+1)*log(1 + x)^k/(k*(1 - log(1 + x)^k))).
a(n) = Sum_{k=0..n} Stirling1(n,k)*A000009(k)*k!.

A330388 Expansion of e.g.f. Sum_{k>=1} (-1)^(k + 1) * log(1 + x)^k / (k * (1 - log(1 + x)^k)).

Original entry on oeis.org

1, 0, 7, -37, 338, -2816, 28418, -340334, 5015080, -84244704, 1536606168, -29753884392, 609895549872, -13243687082016, 305507366834832, -7523621131117296, 198844500026698752, -5649686902983730560, 171839087043420258432, -5545292300345590210944
Offset: 1

Views

Author

Ilya Gutkovskiy, Dec 12 2019

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 20; CoefficientList[Series[Sum[(-1)^(k + 1) Log[1 + x]^k/(k (1 - Log[1 + x]^k)), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]! // Rest
    Table[Sum[StirlingS1[n, k] (k - 1)! Sum[Mod[d, 2] d, {d, Divisors[k]}], {k, 1, n}], {n, 1, 20}]
    nmax = 20; Rest[CoefficientList[Series[Sum[Log[1 + Log[1 + x]^k], {k, 1, nmax}], {x, 0, nmax}], x] * Range[0, nmax]!] (* Vaclav Kotesovec, Dec 15 2019 *)

Formula

E.g.f.: -Sum_{k>=1} log(1 - log(1 + x)^(2*k - 1)).
E.g.f.: A(x) = log(B(x)), where B(x) = e.g.f. of A298905.
exp(Sum_{n>=1} a(n) * (exp(x) - 1)^n / n!) = g.f. of A000009.
a(n) = Sum_{k=1..n} Stirling1(n,k) * (k - 1)! * A000593(k).
E.g.f.: Sum_{k>=1} log(1 + log(1 + x)^k). - Vaclav Kotesovec, Dec 15 2019
Conjecture: a(n) ~ n! * (-1)^(n+1) * Pi^2 * exp(n) / (24 * (exp(1) - 1)^(n+1)). - Vaclav Kotesovec, Dec 16 2019
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