A038052 -id:A038052 - cp's OEIS frontend

A048802 Number of labeled rooted trees of nonempty sets with n points. (Each node is a set of 1 or more points.)

1, 3, 16, 133, 1521, 22184, 393681, 8233803, 198342718, 5408091155, 164658043397, 5537255169582, 203840528337291, 8153112960102283, 352079321494938344, 16325961781591781401, 809073412162081974237, 42674870241038732398720, 2386963662244981472850709

Offset: 1

Christian G. Bower, Mar 15 1999

nonn

			G.f. = x + 3*x^2 + 16*x^3 + 133*x^4 + 1521*x^5 + 22184*x^6 + 393681*x^7 + ...

Vincenzo Librandi, Table of n, a(n) for n = 1..200
F. Chapoton, F. Hivert, J.-C. Novelli, A set-operad of formal fractions and dendriform-like sub-operads, arXiv preprint arXiv:1307.0092 [math.CO], 2013.
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 861
B. R. Jones, On tree hook length formulas, Feynman rules and B-series, Master's thesis, Simon Fraser University, 2014.
Index entries for sequences related to rooted trees

Cf. A036249, A038052, A058863, A052807.

nn=20;t=Sum[n^(n-1)x^n/n!,{n,1,nn}];Range[0,nn]!CoefficientList[ ComposeSeries[ Series[t,{x,0,nn}],Series[Exp[x]-1 ,{x,0,nn}]],x]  (* Geoffrey Critzer, Sep 16 2012 *)

{a(n) = sum( k=1, n, stirling(n, k, 2) * k^(k - 1))}; /* Michael Somos, Jun 09 2012 */

{a(n) = n! * polcoeff( serreverse( log(1 + x*exp(-x +x*O(x^n))) ),n)}
for(n=1,30,print1(a(n),", ")) \\ Paul D. Hanna, Jan 24 2016

E.g.f.: B(exp(x)-1) where B is e.g.f. of A000169.
E.g.f.: Series_Reversion( log(1 + x*exp(-x)) ). - Paul D. Hanna, Jan 24 2016
a(n) = Sum_{k=1..n} Stirling2(n, k)*k^(k-1). - Vladeta Jovovic, Sep 17 2003
Stirling transform of A000169. - Michael Somos, Jun 09 2012
a(n) ~ sqrt(1+exp(1)) * n^(n-1) / (exp(n) * (log(1+exp(-1)))^(n-1/2)). - Vaclav Kotesovec, Feb 17 2014

A282190 E.g.f.: 1/(1 + LambertW(1-exp(x))), where LambertW() is the Lambert W-function.

Original entry on oeis.org

1, 1, 5, 40, 447, 6421, 112726, 2338799, 55990213, 1519122598, 46066158817, 1543974969769, 56677405835276, 2261488166321697, 97455090037460785, 4510770674565054000, 223183550978156866507, 11755122645815049275521, 656670295411196201190366, 38779502115371642484125915, 2413908564514961126280655257

Offset: 0

Ilya Gutkovskiy, Feb 08 2017

Stirling transform of A000312.

			E.g.f.: A(x) = 1 + x/1! + 5*x^2/2! + 40*x^3/3! + 447*x^4/4! + 6421*x^5/5! + 112726*x^6/6! + ...

G. C. Greubel, Table of n, a(n) for n = 0..375
M. Bernstein and N. J. A. Sloane, Some canonical sequences of integers, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210. [Link to arXiv version]
M. Bernstein and N. J. A. Sloane, Some canonical sequences of integers, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210. [Link to Lin. Alg. Applic. version together with omitted figures]
Eric Weisstein's MathWorld, Stirling Transform

Cf. A000312, A000670, A038052, A048802, A052880, A308490, A308491.

b:= proc(n, m) option remember;
     `if`(n=0, m^m, m*b(n-1, m)+b(n-1, m+1))
    end:
a:= n-> b(n, 0):
seq(a(n), n=0..23);  # Alois P. Heinz, Aug 03 2021

Range[0, 20]! CoefficientList[Series[1/(1 + ProductLog[1 - Exp[x]]), {x, 0, 20}], x]
Join[{1}, Table[Sum[StirlingS2[n, k] k^k, {k, 1, n}], {n, 1, 20}]]

x='x+O('x^50); Vec(serlaplace(1/(1 + lambertw(1-exp(x))))) \\ G. C. Greubel, Nov 12 2017

a(0) = 1, a(n) = Sum_{k=1..n} Stirling2(n,k)*k^k.

a(n) ~ n^n / (sqrt(1+exp(1)) * (log(1+exp(-1)))^(n+1/2) * exp(n)). - Vaclav Kotesovec, Feb 17 2017

A035051 Number of labeled rooted connected graphs where every block is a complete graph.

Original entry on oeis.org

0, 1, 2, 12, 116, 1555, 26682, 558215, 13781448, 392209380, 12641850510, 455198725025, 18109373455164, 788854833679549, 37343190699472322, 1908871649888004240, 104789417805394595600, 6148562290130009617619

Offset: 0

Christian G. Bower, Oct 15 1998

Equivalently, rooted labeled spanning trees in the complete hypergraph on n vertices (all hyperedges having cardinality 2 or greater).

Warren D. Smith and David Warme, Paper in preparation, 2002.

T. D. Noe, Table of n, a(n) for n=0..100
Roland Bacher, On the enumeration of labelled hypertrees and of labelled bipartite trees, arXiv:1102.2708 [math.CO], 2011.
Maryam Bahrani and Jérémie Lumbroso, Enumerations, Forbidden Subgraph Characterizations, and the Split-Decomposition, arXiv:1608.01465, 2016.
I. M. Gessel and L. H. Kalikow, Hypergraphs and a functional equation...
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 864
D. M. Warme, Spanning Trees in Hypergraphs with Applications to Steiner Trees. PhD thesis, University of Virginia, 1998.

Cf. A007549, A007563, A030019, A038052, A038053, A030438. A052888, A210586.

f[n_] := Sum[ n^i*StirlingS2[n - 1, i], {i, 0, n - 1}]; Array[f, 18, 0] (* Robert G. Wilson v, Apr 05 2012 *)
Table[If[n == 0, 0, BellB[n - 1, n]], {n, 0, 100}] (* Emanuele Munarini, May 23 2014 *)

a(n):=if n=0 then 0 else sum(stirling2(n-1,k)*n^k,k,0,n);
makelist(a(n),n,0,12); /* Emanuele Munarini, May 23 2014 */

for(n=0,30, print1(sum(k=0,n-1, stirling(n-1,k,2)*n^k), ", ")) \\ G. C. Greubel, Nov 17 2017

Recurrence: a(1) = 1, a(n) = Sum_{k=1}^{n-1} Bell(k) / k! Sum_{a_j > 0, Sum_{j=1}^k a_j = n-1} {{n-1} choose {a_1, a_2, ..., a_k }} \prod_{j=1}^k a(a_j) for n > 1, where Bell(k) = A000110(k). - Warren D. Smith, Feb 23 1998
a(n) = Sum_{i=0...n-1} S(n-1, i) n^i, where S(N, M) are Stirling numbers of the second kind - David Warme, Mar 25 1998
E.g.f. satisfies A(x)=x*exp(exp(A(x))-1).
Let X_{mu} be a Poisson random variable with mean mu: P(X_{mu} = K) = e^{-mu} mu^K / K!. The n-th moment of X_{mu} is E[X_{mu}^n] = sum_{i=0}^n S(n, i) mu^i. Therefore a(n) = E[X_n^{n-1}]. - Langworth Withers, May 25 2000
Dobinski-type formula: a(n) = 1/e^n*sum {k = 0..inf} n^k*k^(n-1)/k!. Cf. A030019 and A052888. For a refinement of this sequence see A210586. - Peter Bala, Apr 05 2012
a(n) ~ exp((1/LambertW(1)-2)*n) * n^(n-1) / (sqrt(1+LambertW(1)) * LambertW(1)^(n-1)). - Vaclav Kotesovec, Jan 22 2014

A036250 Number of trees of nonempty sets with n points. (Each node is a set of 1 or more points.)

Original entry on oeis.org

1, 1, 2, 3, 7, 14, 35, 85, 231, 633, 1845, 5461, 16707, 51945, 164695, 529077, 1722279, 5664794, 18813369, 62996850, 212533226, 721792761, 2466135375, 8471967938, 29249059293, 101440962296, 353289339927, 1235154230060, 4333718587353, 15255879756033

Offset: 0

Christian G. Bower, Nov 15 1998

nonn

Also the number of non-isomorphic connected multigraphs with loops with n edges and multiset density -1, where the multiset density of a multiset partition is the sum of the numbers of distinct vertices in each part minus the number of parts minus the number of vertices. - Gus Wiseman, Nov 28 2018

Alois P. Heinz, Table of n, a(n) for n = 0..1717
Richard J. Mathar, Counting Connected Graphs without Overlapping Cycles, arXiv:1808.06264 [math.CO], 2018.
Gus Wiseman, Non-isomorphic representatives of the a(1) = 2 through a(5) = 35 connected multigraphs with loops with multiset density -1.
Index entries for sequences related to trees

Essentially the same as A036251.

Cf. A000055, A007718, A007719, A038052, A191646, A303837, A321155, A321229, A321254, A321256, A322111.

max = 30; B[] = 1; Do[B[x] = x*Exp[Sum[(B[x^k] + x^k)/k + O[x]^n, {k, 1, n}]] // Normal, {n, 1, max}]; A[x_] = B[x] - B[x]^2/2 + B[x^2]/2; CoefficientList[1 + A[x] + O[x]^max, x] (* Jean-François Alcover, Jan 28 2019 *)

G.f.: B(x) - B^2(x)/2 + B(x^2)/2, where B(x) is g.f. for A036249.

A038051 G.f.: B(x/(1-x)) where B is g.f. of A000169.

Original entry on oeis.org

1, 3, 14, 98, 944, 11642, 175108, 3108310, 63601168, 1473864722, 38152990484, 1091172974102, 34169139856024, 1162736848398010, 42723615842296540, 1685853467536076798, 71101435046807892512, 3191843270961299033762, 151956292916451992949028

Offset: 1

Christian G. Bower, Jan 04 1999

nonn

Vincenzo Librandi, Table of n, a(n) for n = 1..200

Cf. A036249, A038052.

E.g.f. of A048802.

CoefficientList[Series[E^x*(-LambertW[-x]/(1+LambertW[-x])/x), {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Feb 17 2014 *)

E.g.f.: int(exp(x)*(-LambertW(-x)/(1+LambertW(-x))/x), x). a(n) = Sum_{k=0..n-1} binomial(n-1, k)*(k+1)^k. - Vladeta Jovovic, Apr 12 2003

a(n) ~ n^(n-1) * exp(exp(-1)). - Vaclav Kotesovec, Feb 17 2014

Corrected by Christian G. Bower, Mar 15 1999

A323619 Expansion of e.g.f. 1 - LambertW(-log(1+x))*(2 + LambertW(-log(1+x)))/2.

Original entry on oeis.org

1, 1, 0, 2, 3, 44, 260, 3534, 40796, 658440, 11066184, 220005840, 4750650432, 114430365048, 2993377996440, 85208541290040, 2611784941760640, 85941161628865344, 3018822193183216320, 112805065528683216192, 4467115744449046110720, 186900232401341222964480, 8237944325702047624948224

Offset: 0

Ilya Gutkovskiy, Jan 20 2019

nonn

Robert Israel, Table of n, a(n) for n = 0..398

Cf. A000272, A038052, A048994, A277489, A305819.

[n le 0 select 1 else (&+[StirlingFirst(n,k)*k^(k-2): k in [1..n]]): n in [0..25]]; // G. C. Greubel, Feb 07 2019

seq(n!*coeff(series(1-LambertW(-log(1+x))*(2+LambertW(-log(1+x)))/2, x=0,23),x,n),n=0..22); # Paolo P. Lava, Jan 28 2019

nmax = 22; CoefficientList[Series[1 - LambertW[-Log[1 + x]] (2 + LambertW[-Log[1 + x]])/2, {x, 0, nmax}], x] Range[0, nmax]!
Join[{1}, Table[Sum[StirlingS1[n, k] k^(k - 2), {k, n}], {n, 22}]]

{a(n) = if(n==0,1, sum(k=1,n, stirling(n,k,1)*k^(k-2)))};
vector(25, n, n--; a(n)) \\ G. C. Greubel, Feb 07 2019

[1] + [sum((-1)^(k+n)*stirling_number1(n,k)*k^(k-2) for k in (1..n)) for n in (1..25)] # G. C. Greubel, Feb 07 2019

a(n) = Sum_{k=0..n} Stirling1(n,k)*A000272(k).

a(n) ~ n^(n-2) / ((exp(exp(-1))-1)^(n - 3/2) * exp(n - 3*(1 - exp(-1))/2)). - Vaclav Kotesovec, Jan 20 2019

A350746 Triangle read by rows: T(n,k) is the number of labeled quasi-loop-threshold graphs on vertex set [n] with k components, for n >= 1 and 1 <= k <= n.

Original entry on oeis.org

2, 3, 4, 16, 18, 8, 133, 155, 72, 16, 1521, 1810, 910, 240, 32, 22184, 26797, 14145, 4180, 720, 64, 393681, 480879, 262514, 83230, 16520, 2016, 128, 8233803, 10144283, 5675866, 1888873, 409360, 58912, 5376, 256

Offset: 1

David Galvin, Jan 13 2022

The family of quasi-loop-threshold graphs is the smallest family of looped graphs that contains K_1 (a single vertex) and K^loop_1 (a single looped vertex), and is closed under taking unions and adding looped dominating vertices (looped, and adjacent to everything previously added).

			Triangle begins:
        2;
        3,        4;
       16,       18,       8;
      133,      155,      72,      16;
     1521,     1810,     910,     240,     32;
    22184,    26797,   14145,    4180,    720,    64;
   393681,   480879,  262514,   83230,  16520,  2016,  128;
  8233803, 10144283, 5675866, 1888873, 409360, 58912, 5376, 256;
  ...

D. Galvin, G. Wesley and B. Zacovic, Enumerating threshold graphs and some related graph classes, arXiv:2110.08953 [math.CO], 2021.

Row sums are A038052.

Except at n=1, the first column is A048802 (A048802 takes value 1 at n=1).

qltconn[0] = 0; qltconn[1] = 2; qltconn[n_] := qltconn[n] = Sum[StirlingS2[n, k]*(k^(k - 1)), {k, 1, n}] (*qltconn is the number of connected quasi loop threshold graphs on n vertices*); T[n_, l_] := T[n, l] := (Factorial[n]/Factorial[l])*Coefficient[(Sum[(qltconn[k]*(x^k))/Factorial[k], {k, 1, n}])^l, x, n]; Table[T[n, l], {n, 1, 12}, {l, 1, n}]

See Section 1.4 of Galvin, Wesley and Zacovic link for two methods to compute T(n,k).

cp's OEIS Frontend

A048802 Number of labeled rooted trees of nonempty sets with n points. (Each node is a set of 1 or more points.)

Views

Author

Keywords

Examples

Links

Crossrefs

Programs

Mathematica

PARI

PARI

Formula

A282190 E.g.f.: 1/(1 + LambertW(1-exp(x))), where LambertW() is the Lambert W-function.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Maple

Mathematica

PARI

Formula

A035051 Number of labeled rooted connected graphs where every block is a complete graph.

Views

Author

Keywords

Comments

References

Links

Crossrefs

Programs

Mathematica

Maxima

PARI

Formula

A036250 Number of trees of nonempty sets with n points. (Each node is a set of 1 or more points.)

Views

Author

Keywords

Comments

Links

Crossrefs

Programs

Mathematica

Formula

A038051 G.f.: B(x/(1-x)) where B is g.f. of A000169.

Views

Author

Keywords

Links

Crossrefs

Programs

Mathematica

Formula

Extensions

A323619 Expansion of e.g.f. 1 - LambertW(-log(1+x))*(2 + LambertW(-log(1+x)))/2.

Views

Author

Keywords

Links

Crossrefs

Programs

Magma

Maple

Mathematica

PARI

Sage

Formula

A350746 Triangle read by rows: T(n,k) is the number of labeled quasi-loop-threshold graphs on vertex set [n] with k components, for n >= 1 and 1 <= k <= n.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs