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 1-5 of 5 results.

A069768 Signature-permutation of Catalan bijection "Knack".

Original entry on oeis.org

0, 1, 3, 2, 8, 7, 6, 4, 5, 22, 21, 20, 17, 18, 19, 16, 14, 9, 10, 15, 11, 12, 13, 64, 63, 62, 58, 59, 61, 57, 54, 45, 46, 55, 48, 49, 50, 60, 56, 53, 44, 47, 51, 42, 37, 23, 24, 38, 25, 26, 27, 52, 43, 39, 28, 29, 40, 30, 31, 32, 41, 33, 34, 35, 36, 196, 195, 194, 189, 190
Offset: 0

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Author

Antti Karttunen, Apr 16 2002; entry revised Dec 20 2008

Keywords

Comments

This automorphism of binary trees first swaps the left and right subtree of the root and then proceeds recursively to the (new) left subtree, to do the same operation there. This is one of those Catalan bijections which extend to a unique automorphism of the infinite binary tree, which in this case is A153142. See further comments there and in A153141.
This bijection, Knack, is a ENIPS-transformation of the simple swap: ENIPS(*A069770) (i.e., row 1 of A122204). Furthermore, Knack and Knick (the inverse, A069767) have a special property, that FORK and KROF transforms (explained in A122201 and A122202) transform them to their own inverses, i.e., to each other: FORK(Knick) = KROF(Knick) = Knack and FORK(Knack) = KROF(Knack) = Knick, thus this occurs also as row 1 in A122288 and naturally, the double-fork fixes both, e.g., FORK(FORK(Knack)) = Knack.
Note: the name in Finnish is "Naks".

References

  • A. Karttunen, paper in preparation.

Links

Crossrefs

Inverse permutation: "Knick", A069767. "n-th powers" (i.e. n-fold applications), from n=2 to 6: A073291, A073293, A073295, A073297, A073299.
In range [A014137(n-1)..A014138(n-1)] of this permutation, the number of cycles is A073431, number of fixed points: A036987 (Fixed points themselves: A084108), Max. cycle size & LCM of all cycle sizes: A011782. See also: A074080.
A127302(a(n)) = A127302(n) for all n. a(n) = A057162(A057508(n)) = A069769(A057162(n))
Row 1 of A122204 and A122288, row 21 of A122285 and A130402, row 8 of A073200.
See also bijections A073287, A082346, A082347, A082350, A130342.

A069767 Signature-permutation of Catalan bijection "Knick".

Original entry on oeis.org

0, 1, 3, 2, 7, 8, 6, 5, 4, 17, 18, 20, 21, 22, 16, 19, 15, 12, 13, 14, 11, 10, 9, 45, 46, 48, 49, 50, 54, 55, 57, 58, 59, 61, 62, 63, 64, 44, 47, 53, 56, 60, 43, 52, 40, 31, 32, 41, 34, 35, 36, 42, 51, 39, 30, 33, 38, 29, 26, 27, 37, 28, 25, 24, 23, 129, 130, 132, 133, 134
Offset: 0

Views

Author

Antti Karttunen, Apr 16 2002; entry revised Dec 20 2008

Keywords

Comments

This automorphism of binary trees first swaps the left and right subtree of the root and then proceeds recursively to the (new) right subtree, to do the same operation there. This is one of those Catalan bijections which extend to a unique automorphism of the infinite binary tree, which in this case is A153141. See further comments there.
This bijection, Knick, is a SPINE-transformation of the simple swap: SPINE(*A069770) (i.e., row 1 of A122203). Furthermore, Knick and Knack (the inverse, *A069768) have a special property, that FORK and KROF transforms (explained in A122201 and A122202) transform them to their own inverses, i.e., to each other: FORK(Knick) = KROF(Knick) = Knack and FORK(Knack) = KROF(Knack) = Knick, thus this occurs also as a row 1 in A122287 and naturally, the double-fork fixes both, e.g., FORK(FORK(Knick)) = Knick. There are also other peculiar properties.
Note: the name in Finnish is "Niks".

References

  • A. Karttunen, paper in preparation.

Links

Crossrefs

Inverse permutation: "Knack", A069768. "n-th powers" (i.e. n-fold applications), from n=2 to 6: A073290, A073292, A073294, A073296, A073298.
In range [A014137(n-1)..A014138(n-1)] of this permutation, the number of cycles is A073431, number of fixed points: A036987 (Fixed points themselves: A084108), Max. cycle size & LCM of all cycle sizes: A011782. See also: A074080.
A127302(a(n)) = A127302(n) for all n. a(n) = A057508(A057161(n)) = A057161(A069769(n)).
Row 1 of A122203 and A122287, row 15 of A122286 and A130403, row 6 of A073200.
See also bijections A073286, A082345, A082348, A082349, A130341.

A084107 A014486-encoding of "Complete Binary Trees".

Original entry on oeis.org

0, 2, 50, 14642, 1016674610, 4489135110542145842, 83940259113354708787282267381662562610, 28755706180189132304920279902696353117047700481289459579932708798287463397682
Offset: 0

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Author

Antti Karttunen, May 13 2003

Keywords

Comments

"Complete" or "full binary tree" refers to a unique binary tree of (2^n)-1 nodes with its 2^(n-1) leaves all on the same height (or depth) n-1 (when the root is at height 0). These are depicted at A073346. This differs from "completely binary tree", with which some authors refer to trees more akin to the trees encoded by A080299.

Links

Crossrefs

a(n) = A014486(A084108(n)). Subset of A083941.

A083940 A014486-indices of symmetric binary trees.

Original entry on oeis.org

0, 1, 6, 43, 51, 389, 416, 477, 504, 551, 4102, 4191, 4397, 4485, 4649, 5100, 5187, 5393, 5481, 5645, 5964, 6051, 6215, 6489, 47404, 47700, 48403, 48697, 49268, 50833, 51126, 51828, 52120, 52691, 53829, 54120, 54690, 55690, 59334, 59627, 60328
Offset: 0

Views

Author

Antti Karttunen, May 13 2003

Keywords

Comments

Fixed points of permutation A057163.

Crossrefs

a(n) = A080300(A083941(n)). Cf. A083938, A084108.

Formula

a(0)=0, a(n)=A072764bi(n-1, A057163(n-1)).

A083942 Positions of breadth-first-wise encodings (A002542) of the complete binary trees (A084107) in A014486.

Original entry on oeis.org

0, 1, 8, 625, 13402696, 19720133460129649, 126747521841153485025455279433135688, 15141471069096667541622192498608408980462133134430650704600552060872705905
Offset: 0

Views

Author

Antti Karttunen, May 13 2003

Keywords

Links

Crossrefs

Cf. A014138 (partial sums of Catalan numbers), A000108 (Catalan Numbers).

Formula

a(n) = A057118(A084108(n)).
a(n) = A080300(A002542(n)) [provided that 2^((2^n)-1)*((2^((2^n)-1))-1) is indeed the formula for A002542].
Conjecture: a(n) = A014138(2^n-2) for n>0. - Alexander Adamchuk, Nov 10 2007
Conjecture: a(n) = Sum_{k=1..2^n-1} A000108(k). - Alexander Adamchuk, Nov 10 2007
Let h(n) = -((C(2*n,n)*hypergeom([1,1/2+n],[2+n],4))/(1+n)+I*sqrt(3)/2+1/2). Assuming Adamchuk's conjecture a(n) = h(2^n) and A014138(n) = h(n+1). - Peter Luschny, Mar 09 2015
Showing 1-5 of 5 results.

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