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 1-7 of 7 results.

A326324 a(n) = A_{5}(n) where A_{m}(x) are the Eulerian polynomials as defined in A326323.

Original entry on oeis.org

1, 1, 6, 46, 456, 5656, 84336, 1467376, 29175936, 652606336, 16219458816, 443419545856, 13224580002816, 427278468668416, 14867050125981696, 554245056343668736, 22039796215883268096, 931198483176870608896, 41658202699736550014976, 1967160945260218035798016
Offset: 0

Views

Author

Peter Luschny, Jun 27 2019

Keywords

Comments

See A326323 for the more general formulas.

Crossrefs

Programs

  • Maple
    seq(add(combinat:-eulerian1(n,k)*5^k, k=0..n), n=0..20);
    # Alternative:
    egf := 4/(5 - exp(4*x)): ser := series(egf, x, 21):
    seq(k!*coeff(ser, x, k), k=0..20);
  • Mathematica
    a[1] := 1; a[n_] := 4^(n + 1)/5 HurwitzLerchPhi[1/5, -n, 0];
    Table[a[n], {n, 0, 20}]
    (* Alternative: *)
    s[n_] := Sum[StirlingS2[n, j] 4^(n - j) j!, {j, 0, n}];
    Table[s[n], {n, 0, 20}]

Formula

a(n) ~ n!/5 * (4/log(5))^(n+1). - Vaclav Kotesovec, Aug 09 2021
a(0) = 1; a(n) = Sum_{k=1..n} binomial(n,k) * 4^(k-1) * a(n-k). - Ilya Gutkovskiy, Feb 04 2022

Extensions

Corrected after notice from Jean-François Alcover by Peter Luschny, Jul 13 2019

A255927 a(n) = (3/4) * Sum_{k>=0} (3*k)^n/4^k.

Original entry on oeis.org

1, 1, 5, 33, 285, 3081, 40005, 606033, 10491885, 204343641, 4422082005, 105265315233, 2733583519485, 76902684021801, 2329889536156005, 75629701786875633, 2618654297178083085, 96336948993312237561, 3752590641305604502005, 154294551397830418471233, 6677999524135208461382685
Offset: 0

Views

Author

Karol A. Penson, Sep 03 2015

Keywords

Examples

			a(5) = 729*hypergeom([2,2,2,2,2],[1,1,1,1],1/4)/16 = 3081.
		

Crossrefs

Programs

  • Maple
    S:= series(3/(4-exp(3*x)), x, 51):
    seq(coeff(S,x,n)*n!, n=0..50); # Robert Israel, Sep 03 2015
    seq(add(combinat:-eulerian1(n,k)*4^k, k=0..n), n=0..20); # Peter Luschny, Jun 27 2019
  • Mathematica
    a[n_] := 3^(n+1)/4 HurwitzLerchPhi[1/4, -n, 0];
    Table[a[n], {n, 0, 20}] (* Jean-François Alcover, Sep 18 2018 *)
    Eulerian1[0, 0] = 1; Eulerian1[n_, k_] := Sum[(-1)^j (k-j+1)^n Binomial[n+1, j], {j, 0, k+1}]; Table[Sum[Eulerian1[n, k] 4^k, {k, 0, n}], {n, 0, 20}] (* Jean-François Alcover, Jul 13 2019, after Peter Luschny *)
  • PARI
    a(n) = sum(k=0, n, stirling(n,k,2)*k!*3^(n-k)); \\ Michel Marcus, Sep 03 2015

Formula

a(n) = Sum_{k>=0} Stirling2(n,k)*k!*3^(n-k).
E.g.f.: 3/(4-exp(3*x)).
Special values of the generalized hypergeometric function n_F_(n-1):
a(n) = (3^(n+1)/16) * hypergeom([2,2,..2],[1,1,..1],1/4), where the sequence in the first square bracket ("upper" parameters) has n elements all equal to 2 whereas the sequence in the second square bracket ("lower" parameters) has n-1 elements all equal to 1.
Example: a(5) = 729 * hypergeom([2,2,2,2,2],[1,1,1,1],1/4)/16 = 3081.
a(n) is the n-th moment of the discrete weight function W(x) = (3/4)*sum(k>=0, Dirac(x-3*k)/4^k), n>=1.
a(n) ~ n! * 3^(n+1) / ((log(2))^(n+1) * 2^(n+3)). - Vaclav Kotesovec, Jul 09 2018
G.f.: Sum_{j>=0} j!*x^j / Product_{k=1..j} (1 - 3*k*x). - Ilya Gutkovskiy, Apr 04 2019
a(n) = A_{4}(n) where A_{n}(x) are the Eulerian polynomials as defined in A326323. - Peter Luschny, Jun 27 2019

Extensions

a(0)=1 prepended by Alois P. Heinz, Sep 18 2018

A384514 Expansion of e.g.f. 6/(7 - exp(6*x)).

Original entry on oeis.org

1, 1, 8, 78, 960, 14736, 272448, 5881968, 145105920, 4026744576, 124159039488, 4211132779008, 155814875873280, 6245695887446016, 269610827961212928, 12469729905669224448, 615184657168540631040, 32246522356406129197056, 1789714914567248392224768
Offset: 0

Views

Author

Seiichi Manyama, Jun 01 2025

Keywords

Crossrefs

Programs

  • PARI
    a(n) = (-6)^(n+1)*polylog(-n, 7)/7;

Formula

a(n) = (-6)^(n+1)/7 * Li_{-n}(7), where Li_{n}(x) is the polylogarithm function.
a(n) = 6^(n+1) * Sum_{k>=0} k^n * (1/7)^(k+1).
a(n) = Sum_{k=0..n} 6^(n-k) * k! * Stirling2(n,k).
a(n) = (1/7) * Sum_{k=0..n} 7^k * (-6)^(n-k) * k! * Stirling2(n,k) for n > 0.
a(0) = 1; a(n) = Sum_{k=1..n} 6^(k-1) * binomial(n,k) * a(n-k).
a(0) = 1; a(n) = a(n-1) + 7 * Sum_{k=1..n-1} (-6)^(k-1) * binomial(n-1,k) * a(n-k).

A331690 a(n) = Sum_{k=0..n} Stirling2(n,k) * k! * n^(n - k).

Original entry on oeis.org

1, 1, 4, 33, 456, 9445, 272448, 10386817, 503758720, 30202999821, 2189000524800, 188349613075393, 18954958449853440, 2203304642871358741, 292675996808408743936, 44022321302156791898625, 7438113993194856900034560, 1401876939543892434209075581
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 24 2020

Keywords

Crossrefs

Programs

  • Mathematica
    Join[{1}, Table[Sum[StirlingS2[n, k] k! n^(n - k), {k, 0, n}], {n, 1, 17}]]
    Table[SeriesCoefficient[Sum[k! x^k/Product[(1 - n j x), {j, 1, k}], {k, 0, n}], {x, 0, n}], {n, 0, 17}]
    Join[{1}, Table[n^(n + 1) PolyLog[-n, 1/(n + 1)]/(n + 1), {n, 1, 17}]]
  • PARI
    a(n) = sum(k=0, n, stirling(n, k, 2)*k!*n^(n-k)); \\ Michel Marcus, Jan 24 2020

Formula

a(n) = [x^n] Sum_{k>=0} k! * x^k / Product_{j=1..k} (1 - n*j*x).
a(n) = n! * [x^n] n / (1 + n - exp(n*x)) for n > 0.
a(n) = n^(n + 1) * Sum_{k>=1} k^n / (n + 1)^(k + 1) for n > 0.
a(n) ~ n! * n^(n+1) / ((n+1) * log(n+1)^(n+1)). - Vaclav Kotesovec, Jun 06 2022

A332700 A(n, k) = Sum_{j=0..n} j!*Stirling2(n, j)*(k-1)^(n-j), for n >= 0 and k >= 0, read by ascending antidiagonals.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 6, 3, 1, 1, 1, 24, 13, 4, 1, 1, 1, 120, 75, 22, 5, 1, 1, 1, 720, 541, 160, 33, 6, 1, 1, 1, 5040, 4683, 1456, 285, 46, 7, 1, 1, 1, 40320, 47293, 15904, 3081, 456, 61, 8, 1, 1, 1, 362880, 545835, 202672, 40005, 5656, 679, 78, 9, 1, 1
Offset: 0

Views

Author

Peter Luschny, Feb 28 2020

Keywords

Examples

			Array begins:
[0] 1, 1,       1,       1,        1,         1,         1, ...    A000012
[1] 1, 1,       1,       1,        1,         1,         1, ...    A000012
[2] 1, 2,       3,       4,        5,         6,         7, ...    A000027
[3] 1, 6,       13,      22,       33,        46,        61, ...   A028872
[4] 1, 24,      75,      160,      285,       456,       679, ...
[5] 1, 120,     541,     1456,     3081,      5656,      9445, ...
[6] 1, 720,     4683,    15904,    40005,     84336,     158095, ...
[7] 1, 5040,    47293,   202672,   606033,    1467376,   3088765, ...
[8] 1, 40320,   545835,  2951680,  10491885,  29175936,  68958295, ...
[9] 1, 362880,  7087261, 48361216, 204343641, 652606336, 1731875605, ...
       A000142, A000670, A122704,  A255927,   A326324, ...
Seen as a triangle:
[0] [1]
[1] [1, 1]
[2] [1, 1,     1]
[3] [1, 2,     1,     1]
[4] [1, 6,     3,     1,     1]
[5] [1, 24,    13,    4,     1,    1]
[6] [1, 120,   75,    22,    5,    1,   1]
[7] [1, 720,   541,   160,   33,   6,   1,  1]
[8] [1, 5040,  4683,  1456,  285,  46,  7,  1, 1]
[9] [1, 40320, 47293, 15904, 3081, 456, 61, 8, 1, 1]
		

Crossrefs

The matrix transpose of A326323.

Programs

  • Maple
    # Prints array by row.
    A := (n, k) -> add(combinat:-eulerian1(n, j)*k^j, j=0..n):
    seq(print(seq(A(n,k), k=0..10)), n=0..8);
    # Alternative:
    egf := n -> `if`(n=1, 1/(1-x), (n-1)/(n - exp((n-1)*x))):
    ser := n -> series(egf(n), x, 21):
    for n from 0 to 6 do seq(n!*coeff(ser(k), x, n), k=0..9) od;
    # Or:
    A := (n, k) -> if k = 0 or n = 0 then 1 elif k = 1 then n! else
    polylog(-n, 1/k)*(k-1)^(n+1)/k fi:
    for n from 0 to 6 do seq(A(n, k), k=0..9) od;
  • Mathematica
    A332700[n_, k_] := n! + Sum[j! StirlingS2[n, j] (k-1)^(n-j), {j, n-1}];
    Table[A332700[n-k, k], {n, 0, 10}, {k, 0, n}] (* Paolo Xausa, Feb 01 2024 *)
  • Sage
    def T(n, k):
        return sum(factorial(j)*stirling_number2(n, j)*(k-1)^(n-j) for j in range(n+1))
    for n in range(8): print([T(n, k) for k in range(8)])

Formula

A(n, k) = Sum_{j=0..n} E(n, j)*k^j, where E(n, k) = A173018(n, k).
A(n, 1) = n!*[x^n] 1/(1-x).
A(n, k) = n!*[x^n] (k-1)/(k - exp((k-1)*x)) for k != 1.
A(n, k) = PolyLog(-n, 1/k)*(k-1)^(n+1)/k for k >= 2.

A384525 Expansion of e.g.f. 5/(6 - exp(5*x)).

Original entry on oeis.org

1, 1, 7, 61, 679, 9445, 158095, 3088765, 68958295, 1731875605, 48328686175, 1483501074925, 49677478279975, 1802159471217925, 70406303657894575, 2947087948180076125, 131584088098220272375, 6242270620707298139125, 313548981075158413477375
Offset: 0

Views

Author

Seiichi Manyama, Jun 01 2025

Keywords

Crossrefs

Cf. A326323.

Programs

  • PARI
    a(n) = (-5)^(n+1)*polylog(-n, 6)/6;

Formula

a(n) = (-5)^(n+1)/6 * Li_{-n}(6), where Li_{n}(x) is the polylogarithm function.
a(n) = 5^(n+1) * Sum_{k>=0} k^n * (1/6)^(k+1).
a(n) = Sum_{k=0..n} 5^(n-k) * k! * Stirling2(n,k).
a(n) = (1/6) * Sum_{k=0..n} 6^k * (-5)^(n-k) * k! * Stirling2(n,k) for n > 0.
a(0) = 1; a(n) = Sum_{k=1..n} 5^(k-1) * binomial(n,k) * a(n-k).
a(0) = 1; a(n) = a(n-1) + 6 * Sum_{k=1..n-1} (-5)^(k-1) * binomial(n-1,k) * a(n-k).

A368119 Array read by ascending antidiagonals. A(n, k) = Product_{j=0..k-1} (n*j + 1).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 6, 1, 1, 1, 4, 15, 24, 1, 1, 1, 5, 28, 105, 120, 1, 1, 1, 6, 45, 280, 945, 720, 1, 1, 1, 7, 66, 585, 3640, 10395, 5040, 1, 1, 1, 8, 91, 1056, 9945, 58240, 135135, 40320, 1, 1, 1, 9, 120, 1729, 22176, 208845, 1106560, 2027025, 362880, 1
Offset: 0

Views

Author

Peter Luschny, Dec 18 2023

Keywords

Comments

A(n, k) is the number of increasing (n + 1)-ary trees on k vertices. (Following a comment of David Callan in A007559.)

Examples

			Array A(n, k) starts:
  [0] 1, 1, 1,   1,    1,      1,       1,         1, ...  A000012
  [1] 1, 1, 2,   6,   24,    120,     720,      5040, ...  A000142
  [2] 1, 1, 3,  15,  105,    945,   10395,    135135, ...  A001147
  [3] 1, 1, 4,  28,  280,   3640,   58240,   1106560, ...  A007559
  [4] 1, 1, 5,  45,  585,   9945,  208845,   5221125, ...  A007696
  [5] 1, 1, 6,  66, 1056,  22176,  576576,  17873856, ...  A008548
  [6] 1, 1, 7,  91, 1729,  43225, 1339975,  49579075, ...  A008542
  [7] 1, 1, 8, 120, 2640,  76560, 2756160, 118514880, ...  A045754
  [8] 1, 1, 9, 153, 3825, 126225, 5175225, 253586025, ...  A045755
		

Crossrefs

Programs

  • SageMath
    def A(n, k): return n**k * rising_factorial(1/n, k) if n > 0 else 1
    for n in range(9): print([A(n, k) for k in range(8)])

Formula

Let rf(n, k) denote the rising factorial and ff(n,k) the falling factorial.
A(n, k) = n^k * rf(1/n, k) if n > 0 else 1.
A(n, k) = (-n)^k * ff(-1/n, k) if n > 0 else 1.
A(n, k) = (n^k * Gamma(k + 1/n)) / Gamma(1/n) for n > 0.
A(n, k) = ((-n)^k * Gamma(1 - 1/n)) / Gamma(1 - 1/n - k) for n > 0.
A(n, k) = k! * [x^k](1 - n*x)^(-1/n).
A(n, k) = [x^k] hypergeom([1, 1/n], [], n*x).
Column n + 1 has a linear recurrence with constant coefficients and signature ((-1)^k*binomial(n+1, n-k) for k=0..n).
Showing 1-7 of 7 results.