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 1-3 of 3 results.

A001192 Number of full sets of size n.

Original entry on oeis.org

1, 1, 1, 2, 9, 88, 1802, 75598, 6421599, 1097780312, 376516036188, 258683018091900, 355735062429124915, 978786413996934006272, 5387230452634185460127166, 59308424712939278997978128490, 1305926814154452720947815884466579
Offset: 0

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Author

Keywords

Comments

A set x is full if every element of x is also a subset of x.
Equals the subpartitions of Eulerian numbers (A000295(n)=2^n-n-1); see A115728 for the definition of subpartitions of a partition. - Paul D. Hanna, Jul 03 2006
Also number of transitive rooted identity trees with n branches. - Gus Wiseman, Dec 21 2016

Examples

			Examples of full sets are 0 := {}, 1 := {0}, 2 := {1,0}, 3a := {2,1,0}, 3b := { {1}, 1, 0}, 4a := { 3a, 2, 1, 0 }.
		

References

  • L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 123, Problem 20.
  • 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).

Crossrefs

Programs

  • Maple
    A001192 := proc(n) option remember: if(n=0)then return 1: fi: return add((-1)^(n-k-1)*binomial(2^k-k,n-k)*procname(k), k=0..n-1); end: seq(A001192(n), n=0..16); # Nathaniel Johnston, Apr 18 2012
  • Mathematica
    max = 16; f[x_] := Sum[a[n]*(x^n/(1+x)^2^n), {n, 0, max}] - 1; cc = CoefficientList[ Series[f[x], {x, 0, max}], x]; Table[a[n], {n, 0, max}] /. First[ Solve[ Thread[cc == 0]]] (* Jean-François Alcover, Nov 02 2011, after Vladeta Jovovic *)
  • PARI
    {a(n)=polcoeff(x^n-sum(k=0, n-1, a(k)*x^k*(1-x+x*O(x^n))^(2^k-k-1) ), n)} \\ Paul D. Hanna, Jul 03 2006

Formula

1 = Sum_{n>=0} a(n)*x^n/(1+x)^(2^n). E.g., 1 = 1/(1+x) + 1*x/(1+x)^2 + 1*x^2/(1+x)^4 + 2*x^3/(1+x)^8 + 9*x^4/(1+x)^16 + 88*x^5/(1+x)^32 + 1802*x^6/(1+x)^64 + ... . - Vladeta Jovovic, May 26 2005
Equivalently, a(n) = (-1)^n*C(2^n+n-1, n) - Sum_{k=0..n-1} a(k)*(-1)^(n-k)*C(2^n+2^k+n-k-1, n-k). - Paul D. Hanna, May 26 2005
G.f.: 1/(1-x) = Sum_{n>=0} a(n)*x^n*(1-x)^(2^n-n-1) = 1*(1-x)^0 + 1*x*(1-x)^0 + 1*x^2*(1-x)^1 + 2*x^3*(1-x)^4 + 9*x^3*(1-x)^11 + ... + a(n)*x^n*(1-x)^(2^n-n-1) + ... . - Paul D. Hanna, Jul 03 2006

Extensions

More terms from Ryan Propper, Jun 13 2005

A182162 Triangle read by rows: number of extensional acyclic digraphs on n labeled nodes with k sources.

Original entry on oeis.org

1, 2, 12, 192, 24, 8160, 2400, 898560, 384480, 14400, 245145600, 126040320, 9777600, 50400, 159035627520, 90043269120, 9660672000, 179222400, 80640, 237882053283840, 141969202744320, 17961178152960, 547498828800, 2586608640, 802369403419852800
Offset: 1

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Author

N. J. A. Sloane, Apr 15 2012

Keywords

Examples

			Triangle begins:
          1;
          2;
         12;
        192,        24;
       8160,      2400;
     898560,    384480,   14400;
  245145600, 126040320, 9777600, 50400;
  ...
		

Crossrefs

Row sums give A182161. First column is A182163. Row lengths are A182220.

Programs

  • Maple
    A001192 := proc(n) option remember: if(n=0)then return 1: fi: return add((-1)^(n-k-1)*binomial(2^k-k,n-k)*procname(k), k=0..n-1); end: A182162 := proc(n,l) local vl: vl := add((-1)^(k-l)*binomial(n,k)*binomial(k,l)*binomial(2^(n-k)-n+k,k)*k!*(n-k)!*A001192(n-k), k=l..n): if(vl = 0)then return NULL: fi: return vl: end: for n from 1 to 10 do seq(A182162(n,l), l=1..n); od; # Nathaniel Johnston, Apr 18 2012
  • Mathematica
    A001192[n_] := A001192[n] = If[n == 0, 1, Sum[(-1)^(n - k - 1)*Binomial[2^k - k, n - k]*A001192[k], {k, 0, n - 1}]];
    A182162[n_, l_] := Module[{vl}, vl = Sum[(-1)^(k - l)* Binomial[n, k]*Binomial[k, l]*Binomial[2^(n - k) - n + k, k]*k!*(n - k)!*A001192[n - k], {k, l, n}]; If[vl == 0, Nothing, vl]];
    Table[A182162[n, l], {n, 1, 10}, {l, 1, n}] // Flatten (* Jean-François Alcover, Mar 09 2023, after Nathaniel Johnston *)

Extensions

a(15)-a(25) from Nathaniel Johnston, Apr 18 2012

A182163 First column of A182162.

Original entry on oeis.org

1, 2, 12, 192, 8160, 898560, 245145600, 159035627520, 237882053283840, 802369403419852800, 6005354444640501350400, 98553538944200922572390400, 3514155297016560613680059596800, 270315783633381492859539110078054400, 44596108353446508026919663976179916800000
Offset: 1

Views

Author

N. J. A. Sloane, Apr 15 2012

Keywords

Crossrefs

Programs

  • Maple
    A001192 := proc(n) option remember: if(n=0)then return 1: fi: return add((-1)^(n-k-1)*binomial(2^k-k,n-k)*procname(k), k=0..n-1); end: A182163 := proc(n) return add((-1)^(k-1)*k*binomial(n,k)*binomial(2^(n-k)-n+k,k)*k!*(n-k)!*A001192(n-k), k=1..n): end: seq(A182163(n), n=1..16); # Nathaniel Johnston, Apr 18 2012
  • Mathematica
    A001192[n_] := A001192[n] = If[n == 0, 1, Sum[(-1)^(n - k - 1)*Binomial[2^k - k, n - k]*A001192[k], {k, 0, n - 1}]];
    a[n_] := Sum[(-1)^(k - 1)*Binomial[n, k]*k*Binomial[2^(n - k) - n + k, k]*k!*(n - k)!*A001192[n - k], {k, 1, n}];
    Table[a[n], {n, 1, 15}] (* Jean-François Alcover, Apr 12 2023, after Nathaniel Johnston *)

Extensions

a(8)-a(15) and removal of a(0) from Nathaniel Johnston, Apr 18 2012
Showing 1-3 of 3 results.