The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A319437 Number of series-reduced palindromic plane trees with n nodes. 2
 1, 0, 1, 1, 1, 2, 3, 4, 7, 10, 15, 23, 35, 52, 81, 121, 185, 280, 427, 645, 985, 1490, 2269, 3440, 5233, 7936, 12071, 18313, 27839, 42256, 64217, 97490, 148137, 224924, 341725, 518923, 788321, 1197178, 1818597, 2761926, 4195381, 6371808, 9678537, 14699771 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 COMMENTS A rooted plane tree is series-reduced if every non-leaf node has at least two branches, and palindromic if the sequence of branches directly under any given node is a palindrome. LINKS Andrew Howroyd, Table of n, a(n) for n = 1..500 Gus Wiseman, The a(15) = 81 series-reduced palindromic plane trees. MATHEMATICA srpanplane[n_]:=If[n==1, {{}}, Join@@Table[Select[Tuples[srpanplane/@c], #==Reverse[#]&], {c, Join@@Permutations/@Select[IntegerPartitions[n-1], Length[#]>1&]}]]; Table[Length[srpanplane[n]], {n, 15}] PROG (PARI) PAL(p)={(1+p)/subst(1-p, x, x^2)} seq(n)={my(p=O(1)); for(i=1, n, p=PAL(x*p)-x*p); Vec(p)} \\ Andrew Howroyd, Sep 19 2018 CROSSREFS Cf. A000108, A000670, A001003, A005043, A008965, A025065, A118376, A242414, A317085, A317086, A317087, A319122, A319436. Sequence in context: A018132 A329758 A100638 * A270659 A159288 A363958 Adjacent sequences: A319434 A319435 A319436 * A319438 A319439 A319440 KEYWORD nonn AUTHOR Gus Wiseman, Sep 18 2018 EXTENSIONS Terms a(27) and beyond from Andrew Howroyd, Sep 19 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 19 23:42 EDT 2024. Contains 372703 sequences. (Running on oeis4.)