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 1-2 of 2 results.

A260325 Triangle read by rows: T(n,k) = logarithmic polynomial A_k^(n)(x) evaluated at x=-1.

Original entry on oeis.org

1, 2, 1, 5, 2, 2, 16, 9, 6, 6, 65, 28, 12, 24, 24, 326, 185, 140, 60, 120, 120, 1957, 846, 750, 120, 360, 720, 720, 13700, 7777, 2562, 5250, 840, 2520, 5040, 5040, 109601, 47384, 47096, 40656, 1680, 6720, 20160, 40320, 40320, 986410, 559953, 378072, 181944, 365904, 15120, 60480, 181440, 362880, 362880
Offset: 1

Views

Author

N. J. A. Sloane, Jul 23 2015

Keywords

Examples

			Triangle begins:
     1;
     2,   1;
     5,   2,   2;
    16,   9,   6,   6;
    65,  28,  12,  24,  24;
   326, 185, 140,  60, 120, 120;
  1957, 846, 750, 120, 360, 720, 720;
  ...
		

Crossrefs

Rows, column sums give A000522, A002747, A002750, A002751.
Main diagonal gives A000142.

Programs

  • Maple
    A260325 := proc(n,r)
        if r = 0 then
            1 ;
        elif n > r+1 then
            0 ;
        else
            add( 1/(r-j*n+1)!,j=1..(r+1)/n) ;
            %*r! ;
        end if;
    end proc:
    for r from 0 to 20 do
        for n from 1 to r+1 do
            printf("%a,",A260325(n,r)) ;
        end do:
        printf("\n") ;
    end do: # R. J. Mathar, Jul 24 2015
  • Mathematica
    T[n_, k_] := Which[n == 0, 1, k > n+1, 0, True, Sum[1/(n-j*k+1)!, {j, 1, (n+1)/k}]*n!];
    Table[T[n, k], {n, 0, 9}, {k, 1, n+1}] // Flatten (* Jean-François Alcover, Apr 25 2023 *)

A002749 Sum of logarithmic numbers.

Original entry on oeis.org

1, 1, 1, 11, -7, 389, -1031, 19039, -24431, 1023497, -4044079, 225738611, -1711460279, 29974303501, 4656373513, 3798866053319, -34131041040991, 2131052083901969, -23678368533941471, 832900320313739227, -4752766287768240359, 148482851420849206421
Offset: 0

Views

Author

Keywords

References

  • J. M. Gandhi, On logarithmic numbers, Math. Student, 31 (1963), 73-83.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Programs

  • Maple
    A002749 := proc(r)
        add(A260324(n,r),n=1..r+1) ;
    end proc:
    seq(A002749(r),r=0..25) ; # R. J. Mathar, Jul 24 2015
  • Mathematica
    m = 22;
    F[x_] = Sum[DivisorSigma[0, n] x^n , {n, 1, m}];
    CoefficientList[F[x]/(x E^x) + O[x]^m, x] Range[0, m-1]! (* Jean-François Alcover, Mar 30 2020 *)

Formula

E.g.f.: F(x)/exp(x)/x where F(x) is o.g.f. for A000005(). - Vladeta Jovovic, Feb 09 2003

Extensions

Corrected and extended by Jeffrey Shallit
Showing 1-2 of 2 results.