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Search: id:A057546
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| A057546 |
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Number of Catalan objects fixed by the gatomorphism A057511/A057512 (deep rotation of general parenthesizations/plane trees). |
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18
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| 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
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OFFSET
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0,3
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COMMENT
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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.
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LINKS
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Index entries for sequences related to parenthesizing
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FORMULA
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a(0)=1, a(n) = A079216(n, 1) = Sum_{d|n} A079216(d-1, n/d)
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MAPLE
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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;
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CROSSREFS
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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.
Sequence in context: A024560 A000039 A053436 this_sequence A138587 A099350 A008627
Adjacent sequences: A057543 A057544 A057545 this_sequence A057547 A057548 A057549
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KEYWORD
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nonn
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AUTHOR
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Antti Karttunen (my_firstname.my_surname(AT)iki.fi) Sep 07 2000. Formula added Jan 03 2003.
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