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.

User: Fabian Nedic

Fabian Nedic's wiki page.

Fabian Nedic has authored 2 sequences.

A253677 Product of decimal digits of n-th term of the Look and Say sequence A005150.

Original entry on oeis.org

1, 1, 2, 2, 4, 12, 24, 36, 216, 1296, 62208, 746496, 107495424, 46438023168, 240734712102912, 8423789045905096704, 5589622068988418728132608, 133524176512370516060034538930176, 581306137722148449693374999786222908342272
Offset: 1

Author

Fabian Nedic, Jan 08 2015

Keywords

Examples

			a(5) = A007954(A005150(5)) = A007954(111221) = 4.
		

Crossrefs

Formula

a(n) = A007954(A005150(n)).

A152684 a(n) is the number of top-down sequences (F_1, F_2, ..., F_n) whereas each F_i is a labeled forest on n nodes, containing i directed rooted trees. F_(i+1) is proper subset of F_i.

Original entry on oeis.org

1, 2, 18, 384, 15000, 933120, 84707280, 10569646080, 1735643790720, 362880000000000, 94121726392108800, 29658516531078758400, 11159820050604594969600, 4942478402320838374195200, 2544989406021562500000000000, 1507645899890367707813511168000
Offset: 1

Author

Fabian Nedic, Dec 10 2008

Keywords

Examples

			a(1) = 1^(1-2)*(1!) = 1.
a(2) = 2^(2-2)*(2!) = 2.
a(3) = 3^(3-2)*(3!) = 18.
		

References

  • Miklos Bona, Introduction to Enumerative Combinatorics, McGraw Hill 2007, Page 276.

Crossrefs

Programs

  • Magma
    [Factorial(n-1)*n^(n-1): n in [1..20]]; // G. C. Greubel, Nov 28 2022
    
  • Maple
    a:= proc(n) option remember; `if`(n=1, 1,
          a(n-1)*(n/(n-1))^(n-3)*n^2)
        end:
    seq(a(n), n=1..20);  # Alois P. Heinz, May 16 2013
  • Mathematica
    Table[n^(n - 1) (n - 1)!, {n, 1, 16}]  (* Geoffrey Critzer, May 10 2013 *)
  • SageMath
    [factorial(n-1)*n^(n-1) for n in range(1,21)] # G. C. Greubel, Nov 28 2022

Formula

a(n) = n^(n-2)*(n!).