A057546 Number of Catalan objects of size n fixed by Catalan Automorphism A057511/A057512 (deep rotation of general parenthesizations/plane trees).

1, 1, 2, 3, 5, 6, 10, 11, 18, 21, 34, 35, 68, 69, 137, 148, 316, 317, 759, 760, 1869, 1915, 4833, 4834, 12796, 12802, 34108, 34384, 92792, 92793, 254752, 254753, 703083, 704956, 1958210, 1958231, 5485330, 5485331, 15427026, 15440591, 43618394, 43618395, 123807695, 123807696, 352561832, 352664217, 1007481494, 1007481495, 2887387009

Offset: 0

Author

Antti Karttunen, Sep 07 2000

Keywords

• nonn

Comments

Greater than A003238 because there exists also parenthesizations like ((() (())) ((()) ())) and (((()) ()) (() (()))) which are fixed by recursive deep rotation, corresponding to Catalan mountain ranges below:

...../\..../\............................./\......../\

../\/\../\/\.....and.its."dual"....../\/\../\/\

./____\/____\......................./____\/____\

It's obvious that a(p) = a(p-1)+1 for all primes p.

Links

• Index entries for sequences related to parenthesizing

Crossrefs

The first row of A079216. The leftmost edge of the triangle A079217 and also its row sums shifted by one. Occurs for first time in A073202 as row 12. Cf. A057513, A079223-A079227, A034731, A003238.

Programs

Maple

with(numtheory,divisors); A057546 := proc(n) local d; if(0=n) then RETURN(1); else RETURN(add(A079216bi(d-1,n/d),d=divisors(n))); fi; end;

Formula

a(0)=1, a(n) = A079216(n, 1) = Sum_{d|n} A079216(d-1, n/d). - Antti Karttunen, Jan 03 2003