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 11-20 of 21 results. Next

A101612 n! * Sum[k=floor(n/2)..n, 1/k].

Original entry on oeis.org

3, 11, 26, 154, 684, 5508, 35664, 361296, 3068640, 37383840, 392722560, 5584394880, 69878833920, 1135360800000, 16484477184000, 301158902016000, 4976250951168000, 100951141777920000, 1870345490614272000
Offset: 2

Views

Author

Ralf Stephan, Dec 10 2004

Keywords

Crossrefs

A052767 Expansion of e.g.f.: -(log(1-x))^5.

Original entry on oeis.org

0, 0, 0, 0, 0, 120, 1800, 21000, 235200, 2693880, 32319000, 410031600, 5519487600, 78864820320, 1194924450720, 19166592681600, 324817601472000, 5803921108010880, 109115988701293440, 2154085473710580480, 44566174481427360000, 964537418717406213120, 21799797542483649131520
Offset: 0

Views

Author

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

Keywords

Crossrefs

Column k=5 of A225479.

Programs

  • Maple
    spec := [S,{B=Cycle(Z),S=Prod(B,B,B,B,B)},labeled]: seq(combstruct[count](spec,size=n), n=0..20);
  • Mathematica
    With[{nn=20},CoefficientList[Series[-(Log[1-x])^5,{x,0,nn}],x] Range[0,nn]!] (* Harvey P. Dale, Oct 14 2019 *)
  • PARI
    a(n) = {5!*stirling(n,5,1)*(-1)^(n+1)} \\ Andrew Howroyd, Jul 27 2020

Formula

E.g.f.: log(-1/(-1+x))^5.
Recurrence: a(1)=0, a(0)=0, a(2)=0, a(4)=0, a(3)=0, (-1-5*n-10*n^2-10*n^3-5*n^4-n^5)*a(n+1) + (31+5*n^4+70*n^2+30*n^3+75*n)*a(n+2) + (-125*n-90-60*n^2-10*n^3)*a(n+3) + (10*n^2+65+50*n)*a(n+4) + (-15-5*n)*a(n+5) + a(n+6)=0, a(5)=120.
a(n) = 120*A000482(n) = 5!*Stirling1(n,5)*(-1)^(n+1). - Andrew Howroyd, Jul 27 2020

Extensions

Definition clarified by Harvey P. Dale, Oct 14 2019
Terms a(20) and beyond from Andrew Howroyd, Jul 27 2020

A052779 Expansion of e.g.f.: (log(1-x))^6.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 720, 15120, 231840, 3265920, 45556560, 649479600, 9604465200, 148370508000, 2402005525920, 40797624067200, 726963917097600, 13580328282393600, 265689107448756480, 5437099866285377280, 116229410301685651200, 2591985252922277184000, 60218914823672258142720
Offset: 0

Views

Author

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

Keywords

Comments

Original name: a simple grammar.

Crossrefs

Column k=6 of A225479.

Programs

  • Maple
    spec := [S,{B=Cycle(Z),S=Prod(B,B,B,B,B,B)},labeled]: seq(combstruct[count](spec,size=n), n=0..20);
  • PARI
    a(n) = {6!*stirling(n,6,1)*(-1)^n} \\ Andrew Howroyd, Jul 27 2020

Formula

E.g.f.: log(-1/(-1+x))^6.
Recurrence: {a(1)=0, a(0)=0, a(2)=0, a(4)=0, a(3)=0, a(5)=0, a(6)=720, (1+15*n^2+6*n+6*n^5+15*n^4+20*n^3+n^6)*a(n+1) + (-63-186*n-225*n^2-6*n^5-45*n^4-140*n^3)*a(n+2) + (540*n+120*n^3+375*n^2+15*n^4+301)*a(n+3) + (-390*n-20*n^3-350-150*n^2)*a(n+4) + (140+15*n^2+90*n)*a(n+5) + (-21-6*n)*a(n+6) + a(n+7)}.
a(n) = 720*A001233(n) = 6!*(-1)^n*Stirling1(n,6). - Andrew Howroyd, Jul 27 2020

Extensions

Name changed and terms a(20) and beyond from Andrew Howroyd, Jul 27 2020

A129841 Antidiagonal sums of triangle T defined in A048594: T(j,k) = k! * Stirling1(j,k), 1<= k <= j.

Original entry on oeis.org

1, -1, 4, -12, 52, -256, 1502, -10158, 78360, -680280, 6574872, -70075416, 816909816, -10342968456, 141357740736, -2074340369088, 32530886655168, -542971977209760, 9610316495698416, -179788450082431536, 3544714566466060032
Offset: 1

Views

Author

Paul Curtz, May 22 2007

Keywords

Examples

			First seven rows of T are
[    1 ]
[   -1,      2 ]
[    2,     -6,      6 ]
[   -6,     22,    -36,     24 ]
[   24,   -100,    210,   -240,    120 ]
[ -120,    548,  -1350,   2040,  -1800,    720 ]
[  720,  -3528,   9744, -17640,  21000, -15120,   5040 ]
		

References

  • P. Curtz, Integration numerique des systemes differentiels a conditions initiales. Note no. 12 du Centre de Calcul Scientifique de l'Armement, 1969, 135 pages, p. 61. Available from Centre d'Electronique de L'Armement, 35170 Bruz, France, or INRIA, Projets Algorithmes, 78150 Rocquencourt.
  • P. Curtz, Gazette des Mathematiciens, 1992, no. 52, p. 44.
  • P. Flajolet, X. Gourdon and B. Salvy, Gazette des Mathematiciens, 1993, no. 55, pp. 67-78.

Crossrefs

Cf. A048594 (T read by rows), A075181 (T unsigned with rows read backwards), A006252 (row sums of T), A000142 (main diagonal of T), A001286 (unsigned first subdiagonal of T). Unsigned values of second through sixth column of T are in A052517, A052748, A052753, A052767, A052779 resp.

Programs

  • Magma
    m:=21; T:=[ [ Factorial(k)*StirlingFirst(j, k): k in [1..j] ]: j in [1..m] ]; [ &+[ T[j-k+1][k]: k in [1..(j+1) div 2] ]: j in [1..m] ]; // Klaus Brockhaus, Jun 03 2007
  • Mathematica
    m = 21; t[j_, k_] := k!*StirlingS1[j, k]; Total /@ Table[ t[j-k+1, k], {j, 1, m}, {k, 1, Quotient[j+1, 2]}] (* Jean-François Alcover, Aug 13 2012, translated from Klaus Brockhaus's Magma program *)

Formula

E.g.f. for k-th column (k>=1): log(1+x)^k. For further formulas see the references.

Extensions

Edited and extended by Klaus Brockhaus, Jun 03 2007

A304654 a(n) = (n!)^2 * Sum_{k=1..n-1} 1/(k^2*(n-k)).

Original entry on oeis.org

0, 0, 4, 27, 328, 6500, 192216, 7952112, 438941952, 31185057024, 2772643115520, 301622403456000, 39413353102848000, 6091955683706880000, 1099401414283210752000, 229088914497045356544000, 54589580461769879715840000, 14750581694440372638842880000
Offset: 0

Views

Author

Vaclav Kotesovec, May 16 2018

Keywords

Crossrefs

Programs

  • Mathematica
    Table[(n!)^2 * Sum[1/(k^2*(n-k)), {k, 1, n-1}], {n, 0, 20}]

Formula

Recurrence: (2*n - 3)*a(n) = (6*n^3 - 25*n^2 + 33*n - 12)*a(n-1) - (n-2)^2*(6*n^3 - 29*n^2 + 42*n - 15)*a(n-2) + (n-3)^3*(n-2)^3*(2*n - 1)*a(n-3).
a(n)/(n!)^2 ~ Pi^2/(6*n).

A304655 a(n) = (n!)^3 * Sum_{k=1..n-1} 1/(k^3*(n-k)^2).

Original entry on oeis.org

0, 0, 8, 81, 2480, 175000, 23825904, 5563712448, 2051674085376, 1124193889529856, 873600549068759040, 927968580453961728000, 1307864687259363065856000, 2386263863328126193631232000, 5521179117888960788194394112000, 15917227342113559040727019683840000
Offset: 0

Views

Author

Vaclav Kotesovec, May 16 2018

Keywords

Crossrefs

Programs

  • Mathematica
    Table[(n!)^3 * Sum[1/(k^3*(n-k)^2), {k, 1, n-1}], {n, 0, 20}]

Formula

Recurrence: n*(12*n^4 - 108*n^3 + 354*n^2 - 501*n + 260)*a(n) = 2*(n-1)*(24*n^7 - 306*n^6 + 1620*n^5 - 4599*n^4 + 7516*n^3 - 7015*n^2 + 3444*n - 696)*a(n-1) - 6*(n-2)^4*(12*n^7 - 162*n^6 + 906*n^5 - 2700*n^4 + 4583*n^3 - 4378*n^2 + 2163*n - 436)*a(n-2) + 2*(n-3)^4*(n-2)^3*(24*n^7 - 342*n^6 + 2004*n^5 - 6201*n^4 + 10816*n^3 - 10497*n^2 + 5208*n - 1048)*a(n-3) - (n-4)^5*(n-3)^5*(n-2)^3*(12*n^4 - 60*n^3 + 102*n^2 - 69*n + 17)*a(n-4).
a(n)/(n!)^3 ~ Zeta(3)/n^2.

A308346 Expansion of e.g.f. 1/(1 - x)^log(1 - x).

Original entry on oeis.org

1, 0, -2, -6, -10, 20, 352, 2772, 18132, 104400, 469608, 238920, -35811048, -730972944, -11436661728, -164609993520, -2294024595312, -31488879303552, -426338226719904, -5626751283423072, -70000948158061728, -745703905072996800, -4142683990211677440, 110386551348875714880
Offset: 0

Views

Author

Ilya Gutkovskiy, May 21 2019

Keywords

Crossrefs

Programs

  • Magma
    m:=30; R:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!( (1-x)^Log(1/(1-x)) )); [Factorial(n-1)*b[n]: n in [1..m]]; // G. C. Greubel, May 21 2019
    
  • Maple
    E:= 1/(1-x)^log(1-x):
    S:= series(E,x,31):
    seq(coeff(S,x,j)*j!,j=0..30); # Robert Israel, May 22 2019
  • Mathematica
    nmax = 23; CoefficientList[Series[1/(1 - x)^Log[1 - x], {x, 0, nmax}], x] Range[0, nmax]!
    Table[Sum[Abs[StirlingS1[n, k]] HermiteH[k, 0], {k, 0, n}], {n, 0, 23}]
    a[n_] := a[n] = -2 Sum[(k - 1)! HarmonicNumber[k - 1] Binomial[n - 1, k - 1] a[n - k], {k, 2, n}]; a[0] = 1; Table[a[n], {n, 0, 23}]
  • PARI
    a(n) = sum(k=0, n, abs(stirling(n, k, 1))*polhermite(k, 0)); \\ Michel Marcus, May 21 2019
    
  • Sage
    m = 30; T = taylor((1-x)^log(1/(1-x)), x, 0, m); [factorial(n)*T.coefficient(x, n) for n in (0..m)] # G. C. Greubel, May 21 2019

Formula

a(n) = Sum_{k=0..n} |Stirling1(n,k)|*A067994(k).

A333371 Exponential convolution of primorial numbers (A002110) with themselves.

Original entry on oeis.org

1, 4, 20, 132, 1116, 12420, 171300, 2884980, 56674380, 1289511300, 34769949060, 1063909626780, 37255008811020, 1470406699982220, 63114539746598340, 2936218980067393020, 150241360192861037100, 8497891914008911514100, 514514062115556069627060
Offset: 0

Views

Author

Ilya Gutkovskiy, Mar 17 2020

Keywords

Crossrefs

Programs

  • Maple
    p:= proc(n) option remember; `if`(n<1, 1, ithprime(n)*p(n-1)) end:
    a:= n-> add(p(i)*p(n-i)*binomial(n, i), i=0..n):
    seq(a(n), n=0..20);  # Alois P. Heinz, Mar 17 2020
  • Mathematica
    primorial[n_] := Product[Prime[k], {k, 1, n}]; a[n_] := Sum[Binomial[n, k] primorial[k] primorial[n - k], {k, 0, n}]; Table[a[n], {n, 0, 18}]

Formula

E.g.f.: (Sum_{k>=0} prime(k)# * x^k / k!)^2, where prime()# = A002110.
a(n) = Sum_{k=0..n} binomial(n,k) * prime(k)# * prime(n-k)#.

A156047 Triangle read by rows: T(n, k) = (n+1)!*(1/k + 1/(n-k+1)).

Original entry on oeis.org

4, 9, 9, 32, 24, 32, 150, 100, 100, 150, 864, 540, 480, 540, 864, 5880, 3528, 2940, 2940, 3528, 5880, 46080, 26880, 21504, 20160, 21504, 26880, 46080, 408240, 233280, 181440, 163296, 163296, 181440, 233280, 408240, 4032000, 2268000, 1728000, 1512000, 1451520, 1512000, 1728000, 2268000, 4032000
Offset: 1

Views

Author

Roger L. Bagula, Feb 02 2009

Keywords

Comments

Row sums are (n+1)*A052517(n+2) = {4, 18, 88, 500, 3288, 24696, 209088, 1972512, 20531520, ...}.

Examples

			Triangle begins as:
      4;
      9,     9;
     32,    24,    32;
    150,   100,   100,   150;
    864,   540,   480,   540,   864;
   5880,  3528,  2940,  2940,  3528,  5880;
  46080, 26880, 21504, 20160, 21504, 26880, 46080;
		

Crossrefs

Programs

  • GAP
    Flat(List([1..10], n-> List([1..n], k-> (n+1)*Factorial(n+1)/(k*(n-k+1)) ))); # G. C. Greubel, Dec 02 2019
  • Magma
    [(n+1)*Factorial(n+1)/(k*(n-k+1)): k in [1..n], n in [1..10]]; // G. C. Greubel, Dec 02 2019
    
  • Maple
    seq(seq( (n+1)*(n+1)!/(k*(n-k+1)), k=1..n), n=1..10); # G. C. Greubel, Dec 02 2019
  • Mathematica
    Table[(n+1)*(n+1)!/(k*(n-k+1)), {n,10}, {k,n}]//Flatten (* modified by G. C. Greubel, Dec 02 2019 *)
  • PARI
    T(n,k) = (n+1)*(n+1)!/(k*(n-k+1)); \\ G. C. Greubel, Dec 02 2019
    
  • Sage
    [[(n+1)*factorial(n+1)/(k*(n-k+1)) for k in (1..n)] for n in (1..10)] # G. C. Greubel, Dec 02 2019
    

Formula

T(n, k) = (n+1)*(n+1)!/(k*(n-k+1)).
Sum_{k=1..n} T(n,k) = 2*(n+1)!*H(n), where H(n) is the harmonic number. - G. C. Greubel, Dec 02 2019

Extensions

Offset changed by G. C. Greubel, Dec 02 2019

A377394 Expansion of e.g.f. (1 - log(1-x))^3.

Original entry on oeis.org

1, 3, 9, 30, 120, 582, 3354, 22488, 172320, 1487208, 14284296, 151179696, 1748521296, 21945019392, 297077918976, 4315269544704, 66952906801920, 1105127533048320, 19337110495511040, 357542547031249920, 6965984564179246080, 142638952766943744000, 3062533108375448064000
Offset: 0

Views

Author

Seiichi Manyama, Oct 27 2024

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, 3, k!*binomial(3, k)*abs(stirling(n, k, 1)));

Formula

a(n) = Sum_{k=0..3} k! * binomial(3,k) * |Stirling1(n,k)|.
a(0) = 1; a(n) = Sum_{k=1..n} (4 * k/n - 1) * (k-1)! * binomial(n,k) * a(n-k).
Previous Showing 11-20 of 21 results. Next