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 13 results. Next

A036370 Triangle of coefficients of generating function of ternary rooted trees of height at most n.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 4, 5, 4, 4, 3, 2, 1, 1, 1, 1, 1, 2, 4, 7, 12, 20, 31, 47, 70, 99, 137, 184, 239, 300, 369, 432, 498, 551, 594, 614, 624, 601, 570, 514, 453, 378, 312, 238, 181, 128, 89, 56, 37, 20, 12, 6, 3, 1, 1
Offset: 0

Views

Author

N. J. A. Sloane, Eric Rains (rains(AT)caltech.edu)

Keywords

Examples

			1;
1, 1;
1, 1, 1, 1, 1;
1, 1, 1, 2, 3, 4, 4, 5, 4, 4, 3, 2, 1, 1;
...
		

Crossrefs

Cf. A036437.

Programs

  • Maple
    T:= proc(n) option remember; local f, g;
          if n=0 then 1
        else f:= z-> add([T(n-1)][i]*z^(i-1), i=1..nops([T(n-1)]));
             g:= expand(1 +z*(f(z)^3/6 +f(z^2)*f(z)/2 +f(z^3)/3));
             seq(coeff(g, z, i), i=0..degree(g, z))
          fi
        end:
    seq(T(n), n=0..5); # Alois P. Heinz, Sep 26 2011
  • Mathematica
    T[n_] := T[n] = Module[{f, g}, If[n == 0, {1}, f[z_] = Sum[T[n-1][[i]]*z^(i-1), {i, 1, Length[T[n-1]]}]; g = Expand[1+z*(f[z]^3/6+f[z^2]*f[z]/2+f[z^3]/3)]; Table[Coefficient [g, z, i], {i, 0, Exponent[g, z]}]]]; Table[T[n], {n, 0, 5}] // Flatten (* Jean-François Alcover, Mar 10 2014, after Alois P. Heinz *)

Formula

T_{i+1}(z) = 1 +z*(T_i(z)^3/6 +T_i(z^2)*T_i(z)/2 +T_i(z^3)/3); T_0(z) = 1.

A287211 The number of plane rooted complete ternary trees with 2n+1 unlabeled leaves (hence n internal nodes including the root where n starts at 0) satisfying these two conditions: (1) if one of the three children of any internal node is the greatest in deglex order then that child is not the leftmost child; (2) if one of the three children of any internal node is the smallest in deglex order then that child is not the rightmost child. Deglex order refers to degree-lexicographical order defined inductively on the number of leaves (see details under Comments).

Original entry on oeis.org

1, 1, 2, 6, 21, 78, 308, 1264, 5332, 22994, 100896, 449004
Offset: 0

Views

Author

Murray R. Bremner, May 21 2017

Keywords

Comments

"Plane" means "embedded in the plane" or (equivalently) the three children of each internal node (including the root) are ordered left, middle, right. Deglex order on trees with 2n+1 leaves is defined as follows: to compare two such trees T and U with children T_1, T_2, T_3 and U_1, U_2, U_3, first find the least index 1 <= i <= 3 for T_i <> U_i, then compare T_i and U_i in deglex order already defined inductively on trees with fewer than 2n+1 leaves; note that this requires comparing trees with different numbers of leaves, so we say that T_i precedes U_i if either (i) T_i has fewer leaves than U_i, or (ii) T_i and U_i have the same number of leaves, and T_i precedes U_i in deglex order.
An alternative description of this sequence: it counts the distinct association types in arity 2n+1 for a ternary operation [a,b,c] satisfying the cyclic-sum relation [a,b,c] + [b,c,a] + [c,a,b] = 0. The two conditions stated under "Name" are necessary to deal with the possibility of repeated factors: [a,a,b], [a,b,a], [b,a,a] where a < b in deglex order, and [a,b,b], [b,a,b], [b,b,a] where a < b in deglex order.
See further details in the comments to the Maple program which is attached as a a-file.

Examples

			Association types for arities 1, 3, 5, 7 are as follows in deglex order. See Links for a-file with association types for arities up to 11.
Arity 1, number of types 1:
a.
Arity 3, number of types 1:
[abc].
Arity 5, number of types 2:
[ab[cde]],
[a[bcd]e].
Arity 7, number of types 6:
[ab[cd[efg]]],
[ab[c[def]g]],
[a[bcd][efg]],
[a[bc[def]]g],
[a[b[cde]f]g],
[[abc]d[efg]].
		

Crossrefs

Programs

  • Maple
    See attached a-file under Links.

A036420 Number of ternary rooted trees with n nodes and height exactly 5.

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 4, 13, 32, 74, 155, 316, 612, 1160, 2126, 3829, 6737, 11672, 19856, 33332, 55112, 90014, 145105, 231200, 363985, 566692, 872274, 1328167, 2000224, 2980316, 4393106, 6407555, 9246741, 13204470, 18657868, 26088224, 36095090
Offset: 0

Views

Author

N. J. A. Sloane, Eric Rains (rains(AT)caltech.edu)

Keywords

Crossrefs

Formula

a(n) = A036373(n) - A036372(n). - Sean A. Irvine, Oct 31 2020

A036421 Number of ternary rooted trees with n nodes and height exactly 6.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 1, 5, 19, 56, 151, 374, 889, 2032, 4529, 9858, 21075, 44320, 91928, 188288, 381392, 764683, 1519026, 2991601, 5844950, 11334761, 21827329, 41755112, 79376196, 149991258, 281805933, 526546799, 978614867, 1809450608
Offset: 0

Views

Author

N. J. A. Sloane, Eric Rains (rains(AT)caltech.edu)

Keywords

Crossrefs

Formula

a(n) = A036374(n) - A036373(n). - Sean A. Irvine, Oct 31 2020

A036422 Number of ternary rooted trees with n nodes and height exactly 7.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 1, 6, 26, 88, 267, 743, 1968, 5006, 12394, 29984, 71289, 166927, 386042, 882887, 1999964, 4491226, 10008151, 22144282, 48681992, 106384313, 231200051, 499868227, 1075542674, 2303703530, 4913213715, 10436198873
Offset: 0

Views

Author

N. J. A. Sloane, Eric Rains (rains(AT)caltech.edu)

Keywords

Crossrefs

Formula

a(n) = A036375(n) - A036374(n). - Sean A. Irvine, Oct 31 2020

A036423 Number of ternary rooted trees with n nodes and height exactly 8.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 1, 7, 34, 129, 432, 1320, 3807, 10505, 28094, 73290, 187579, 472612, 1175580, 2892389, 7050272, 17045235, 40913418, 97571239, 231337744, 545590039, 1280487083, 2991833084, 6961385026, 16135193088, 37263361364
Offset: 0

Views

Author

N. J. A. Sloane, Eric Rains (rains(AT)caltech.edu)

Keywords

Crossrefs

Formula

a(n) = A036376(n) - A036375(n). - Sean A. Irvine, Oct 31 2020

A036424 Number of ternary rooted trees with n nodes and height exactly 9.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 8, 43, 180, 657, 2175, 6746, 19923, 56766, 157273, 426372, 1135812, 2983032, 7742322, 19896231, 50695676, 128224079, 322221166, 805088502, 2001225122, 4951394924, 12198848726, 29938095480, 73210846964
Offset: 0

Views

Author

N. J. A. Sloane, Eric Rains (rains(AT)caltech.edu)

Keywords

Crossrefs

A036419 Number of ternary rooted trees with n nodes and height exactly 4.

Original entry on oeis.org

0, 0, 0, 0, 1, 3, 8, 15, 27, 43, 67, 97, 136, 183, 239, 300, 369, 432, 498, 551, 594, 614, 624, 601, 570, 514, 453, 378, 312, 238, 181, 128, 89, 56, 37, 20, 12, 6, 3, 1, 1
Offset: 0

Views

Author

N. J. A. Sloane, Eric Rains (rains(AT)caltech.edu)

Keywords

Crossrefs

A036425 Number of ternary rooted trees with n nodes and height exactly 10.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 9, 53, 242, 954, 3391, 11220, 35180, 105948, 309175, 880175, 2456272, 6744581, 18273594, 48960386, 129945805, 342114018, 894423399, 2324138696, 6006737947, 15450039511, 39568319805, 100941888863, 256597420700
Offset: 0

Views

Author

N. J. A. Sloane, Eric Rains (rains(AT)caltech.edu)

Keywords

Crossrefs

A036426 Number of ternary rooted trees with n nodes and height exactly 11.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 10, 64, 316, 1336, 5065, 17774, 58840, 186322, 569740, 1694449, 4927345, 14067397, 39554994, 109815312, 301618216, 820875862, 2216564889, 5944589510, 15848003806, 42028780558, 110941624229, 291629971309
Offset: 0

Views

Author

N. J. A. Sloane, Eric Rains (rains(AT)caltech.edu)

Keywords

Crossrefs

Showing 1-10 of 13 results. Next