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 1-10 of 14 results. Next

A290689 Number of transitive rooted trees with n nodes.

Original entry on oeis.org

1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 88, 143, 229, 370, 592, 955, 1527, 2457, 3929, 6304, 10081
Offset: 1

Views

Author

Gus Wiseman, Oct 19 2017

Keywords

Comments

A rooted tree is transitive if every proper terminal subtree is also a branch of the root. First differs from A206139 at a(13) = 143.
Regarding the notation, a rooted tree is a finite multiset of rooted trees. For example, the rooted tree (o(o)(oo)) is short for {{},{{}},{{},{}}}. Each "o" is a leaf. Each pair of parentheses corresponds to a non-leaf node (such as the root). Its contents "(...)" represent a branch. - Gus Wiseman, Nov 16 2024

Examples

			The a(7) = 8 7-node transitive rooted trees are: (o(oooo)), (oo(ooo)), (o(o)((o))), (o(o)(oo)), (ooo(oo)), (oo(o)(o)), (oooo(o)), (oooooo).
		

Crossrefs

The restriction to identity trees (A004111) is A279861, ranks A290760.
These trees are ranked by A290822.
The anti-transitive version is A306844, ranks A324758.
The totally transitive case is A318185 (by leaves A318187), ranks A318186.
A version for integer partitions is A324753, for subsets A324736.
The ordered version is A358453, ranks A358457, undirected A358454.

Programs

  • Mathematica
    nn=18;
    rtall[n_]:=If[n===1,{{}},Module[{cas},Union[Sort/@Join@@(Tuples[rtall/@#]&/@IntegerPartitions[n-1])]]];
    Table[Length[Select[rtall[n],Complement[Union@@#,#]==={}&]],{n,nn}]

Extensions

a(20) from Robert Price, Sep 13 2018
a(21)-a(22) from Robert P. P. McKone, Dec 16 2023

A290760 Matula-Goebel numbers of transitive rooted identity trees (or transitive finitary sets).

Original entry on oeis.org

1, 2, 6, 30, 78, 330, 390, 870, 1410, 3198, 3390, 4290, 7878, 9570, 10230, 11310, 13026, 15510, 15990, 18330, 26070, 30966, 37290, 39390, 40890, 44070, 45210, 65130, 84810, 94830, 98310, 104610, 122070, 124410, 132990, 154830, 159330, 175890, 198330, 201630
Offset: 1

Views

Author

Gus Wiseman, Oct 19 2017

Keywords

Comments

A rooted tree is transitive if every terminal subtree is a branch of the root. A finitary set is transitive if every element is also a subset.

Examples

			Let o = {}. The sequence of transitive finitary sets begins:
1     o
2     {o}
6     {o,{o}}
30    {o,{o},{{o}}}
78    {o,{o},{o,{o}}}
330   {o,{o},{{o}},{{{o}}}}
390   {o,{o},{{o}},{o,{o}}}
870   {o,{o},{{o}},{o,{{o}}}}
1410  {o,{o},{{o}},{{o},{{o}}}}
3198  {o,{o},{o,{o}},{{o,{o}}}}
3390  {o,{o},{{o}},{o,{o},{{o}}}}
4290  {o,{o},{{o}},{{{o}}},{o,{o}}}
7878  {o,{o},{o,{o}},{o,{o,{o}}}}
9570  {o,{o},{{o}},{{{o}}},{o,{{o}}}}
10230 {o,{o},{{o}},{{{o}}},{{{{o}}}}}
11310 {o,{o},{{o}},{o,{o}},{o,{{o}}}}
13026 {o,{o},{o,{o}},{{o},{o,{o}}}}
15510 {o,{o},{{o}},{{{o}}},{{o},{{o}}}}
15990 {o,{o},{{o}},{o,{o}},{{o,{o}}}}
18330 {o,{o},{{o}},{o,{o}},{{o},{{o}}}}
		

Crossrefs

Programs

  • Mathematica
    primeMS[n_]:=If[n===1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    finitaryQ[n_]:=finitaryQ[n]=Or[n===1,With[{m=primeMS[n]},{UnsameQ@@m,finitaryQ/@m}]/.List->And];
    subprimes[n_]:=If[n===1,{},Union@@Cases[FactorInteger[n],{p_,_}:>FactorInteger[PrimePi[p]][[All,1]]]];
    transitaryQ[n_]:=Divisible[n,Times@@subprimes[n]];
    nn=100000;Fold[Select,Range[nn],{finitaryQ,transitaryQ}]

A279861 Number of transitive finitary sets with n brackets. Number of transitive rooted identity trees with n nodes.

Original entry on oeis.org

1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 2, 1, 2, 2, 2, 5, 4, 6, 8, 10, 14, 23, 26, 34, 46, 64, 81, 115, 158, 199, 277, 376, 505, 684, 934, 1241, 1711, 2300, 3123, 4236, 5763, 7814, 10647, 14456, 19662
Offset: 1

Views

Author

Gus Wiseman, Dec 21 2016

Keywords

Comments

A finitary set is transitive if every element is also a subset. Transitive sets are also called full sets.

Examples

			Sequence of transitive finitary sets begins:
1  ()
2  (())
4  (()(()))
7  (()(())((())))
8  (()(())(()(())))
11 (()(())((()))(((()))))
   (()(())((()))(()(())))
12 (()(())((()))(()((()))))
13 (()(())((()))((())((()))))
   (()(())(()(()))((()(()))))
14 (()(())((()))(()(())((()))))
   (()(())(()(()))(()(()(()))))
15 (()(())((()))(((())))(()(())))
   (()(())(()(()))((())(()(()))))
16 (()(())((()))(((())))((((())))))
   (()(())((()))(((())))(()((()))))
   (()(())((()))(()(()))(()((()))))
   (()(())((()))(()(()))((()(()))))
   (()(())(()(()))(()(())(()(()))))
17 (()(())((()))(((())))(()(((())))))
   (()(())((()))(((())))((())((()))))
   (()(())((()))(()(()))(()(()(()))))
   (()(())((()))(()(()))((())((()))))
18 (()(())((()))(((())))((())(((())))))
   (()(())((()))(((())))(()(())((()))))
   (()(())((()))(()(()))((())(()(()))))
   (()(())((()))(()(()))(()(())((()))))
   (()(())((()))((()((()))))(()((()))))
   (()(())((()))(()((())))((())((()))))
		

Crossrefs

Programs

  • Mathematica
    transfins[n_]:=transfins[n]=If[n===1,{{}},Select[Union@@FixedPointList[Complement[Union@@Function[fin,Cases[Complement[Subsets[fin],fin],sub_:>With[{nov=Sort[Append[fin,sub]]},nov/;Count[nov,_List,{0,Infinity}]<=n]]]/@#,#]&,Array[transfins,n-1,1,Union]],Count[#,_List,{0,Infinity}]===n&]];
    Table[Length[transfins[n]],{n,20}]

A137156 Matrix inverse of triangle A137153(n,k) = C(2^k+n-k-1, n-k), read by rows.

Original entry on oeis.org

1, -1, 1, 1, -2, 1, -2, 5, -4, 1, 9, -24, 22, -8, 1, -88, 239, -228, 92, -16, 1, 1802, -4920, 4749, -1976, 376, -32, 1, -75598, 206727, -200240, 84086, -16432, 1520, -64, 1, 6421599, -17568408, 17034964, -7173240, 1413084, -133984, 6112, -128, 1
Offset: 0

Views

Author

Paul D. Hanna, Jan 24 2008

Keywords

Comments

Unsigned column 0 = A001192, number of full sets of size n.

Examples

			Triangle begins:
        1;
       -1,         1;
        1,        -2,        1;
       -2,         5,       -4,        1;
        9,       -24,       22,       -8,       1;
      -88,       239,     -228,       92,     -16,       1;
     1802,     -4920,     4749,    -1976,     376,     -32,    1;
   -75598,    206727,  -200240,    84086,  -16432,    1520,  -64,    1;
  6421599, -17568408, 17034964, -7173240, 1413084, -133984, 6112, -128, 1;
  ...
		

Crossrefs

Cf. A137153 (matrix inverse); unsigned columns: A001192, A137157, A137158, A137159; unsigned row sums: A137160.

Programs

  • PARI
    /* As matrix inverse of A137153: */
    {T(n,k) = local(M=matrix(n+1,n+1,r,c,if(r>=c,binomial(2^(c-1)+r-c-1,r-c)))); if(n
    				
  • PARI
    /* Using the g.f.: */
    {T(n,k) = if(n
    				

Formula

G.f. of column k: 1 = Sum_{n>=0} T(n+k,k)*x^n/(1-x)^(2^(n+k)).

A137157 G.f.: 1 = Sum_{n>=0} a(n)*x^n/(1+x)^(2*2^n).

Original entry on oeis.org

1, 2, 5, 24, 239, 4920, 206727, 17568408, 3003763243, 1030272816360, 707851744149198, 973425618916674288, 2678332881795756783639, 14741522294008025924154864, 162290544340043699103996962253, 3573515596966915773419766367302288, 157376160486791180710467411977740266927
Offset: 0

Views

Author

Paul D. Hanna, Jan 24 2008

Keywords

Comments

Equals unsigned column 1 of triangle A137156.

Crossrefs

Programs

  • PARI
    {a(n)=polcoeff(1-sum(k=0, n-1, a(k)*x^k/(1+x+x*O(x^n))^(2^(k+1)) ), n)}

Extensions

a(15)-a(16) from Alois P. Heinz, Jan 04 2023

A137158 G.f.: 1 = Sum_{n>=0} a(n)*x^n/(1+x)^(4*2^n).

Original entry on oeis.org

1, 4, 22, 228, 4749, 200240, 17034964, 2913479848, 999402129243, 686662003846640, 944294243796543974, 2598186366278914473948, 14300408328085246335179009, 157434326611214704329370130880
Offset: 0

Views

Author

Paul D. Hanna, Jan 24 2008

Keywords

Comments

Equals unsigned column 2 of triangle A137156.

Crossrefs

Programs

  • PARI
    {a(n)=polcoeff(1-sum(k=0, n-1, a(k)*x^k/(1+x+x*O(x^n))^(2^(k+2)) ), n)}

A137159 G.f.: 1 = Sum_{n>=0} a(n)*x^n/(1+x)^(8*2^n).

Original entry on oeis.org

1, 8, 92, 1976, 84086, 7173240, 1227862380, 421296930984, 289484024512093, 398106386971472608, 1095381029276651137560, 6028986377761538637043792, 66373632185586959347740452492, 1461497816340787260620205149915824
Offset: 0

Views

Author

Paul D. Hanna, Jan 24 2008

Keywords

Comments

Equals unsigned column 3 of triangle A137156.

Crossrefs

Programs

  • PARI
    {a(n)=polcoeff(1-sum(k=0, n-1, a(k)*x^k/(1+x+x*O(x^n))^(2^(k+3)) ), n)}

A137160 G.f.: 1 = Sum_{n>=0} a(n)*x^n*(1-x)/(1+x)^(2^n).

Original entry on oeis.org

1, 2, 4, 12, 64, 664, 13856, 584668, 49751520, 8509625760, 2919099754336, 2005648412219832, 2758163973596156000, 7588978611071894509464, 41769719229784446295570112, 459846172005153447271276789620
Offset: 0

Views

Author

Paul D. Hanna, Jan 24 2008

Keywords

Comments

Equals the unsigned row sums of triangle A137156.

Crossrefs

Programs

  • PARI
    {a(n)=polcoeff(1-sum(k=0, n-1, a(k)*x^k*(1-x)/(1+x+x*O(x^n))^(2^k) ), n)}

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

Views

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

A172400 G.f.: 1/(1-x) = (1-x*y) * Sum_{k>=0} Sum_{n>=k} T(n,k)*x^n*y^k/(1+x)^(2^n-2^k).

Original entry on oeis.org

1, 1, 1, 2, 1, 1, 6, 3, 1, 1, 32, 16, 5, 1, 1, 332, 166, 51, 9, 1, 1, 6928, 3464, 1059, 181, 17, 1, 1, 292334, 146167, 44620, 7557, 681, 33, 1, 1, 24875760, 12437880, 3795202, 641035, 57097, 2641, 65, 1, 1, 4254812880, 2127406440, 649054326, 109540639
Offset: 0

Views

Author

Paul D. Hanna, Feb 01 2010

Keywords

Examples

			Triangle begins:
1;
1, 1;
2, 1, 1;
6, 3, 1, 1;
32, 16, 5, 1, 1;
332, 166, 51, 9, 1, 1;
6928, 3464, 1059, 181, 17, 1, 1;
292334, 146167, 44620, 7557, 681, 33, 1, 1;
24875760, 12437880, 3795202, 641035, 57097, 2641, 65, 1, 1;
4254812880, 2127406440, 649054326, 109540639, 9723237, 443921, 10401, 129, 1, 1; ...
Matrix inverse of this triangle begins:
1;
-1,1;
-1,-1,1;
-2,-2,-1,1;
-9,-9,-4,-1,1;
-88,-88,-38,-8,-1,1;
-1802,-1802,-772,-156,-16,-1,1;
-75598,-75598,-32313,-6456,-632,-32,-1,1; ...
in which unsigned column 0 = A001192, number of full sets of size n.
		

Crossrefs

Cf. A001192, columns: A172401, A172402, A172403.

Programs

  • PARI
    {T(n,k)=if(n==k,1,polcoeff(-(1-x)*sum(m=0,n-k-1,T(m+k,k)*x^m/(1+x +x*O(x^n))^(2^(m+k)-2^k)),n-k))}
    
  • PARI
    {T(n,k)=local(M,N); M=matrix(n+1,n+1,r,c,if(r>=c,polcoeff(1/(1-x+O(x^(r-c+1)))^1*(1+x)^(2^(r-1)-2^(c-1)),r-c))); N=matrix(n+1,n+1,r,c,if(r>=c,polcoeff(1/(1-x+O(x^(r-c+1)))^2*(1+x)^(2^(r-1)-2^(c-1)),r-c))); (M^-1*N)[n+1,k+1]}

Formula

Unsigned column 0 of matrix inverse forms A001192, which is the number of full sets of size n.
Showing 1-10 of 14 results. Next