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 1-7 of 7 results.

A072795 A014486-indices of the plane binary trees AND plane general trees whose left subtree is just a stick: \. thus corresponding to the parenthesizations whose first element (of the top-level list) is an empty parenthesization: ().

Original entry on oeis.org

1, 2, 4, 5, 9, 10, 11, 12, 13, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 197, 198, 199
Offset: 0

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Author

Antti Karttunen Jun 12 2002

Keywords

Comments

This sequence is induced by the 'flipped form' of the function 'list': (define (flippedlist x) (cons '() x)) when it acts on symbolless S-expressions encoded by A014486/A063171.

Crossrefs

Gives in A063171 positions of the terms which begin with digits 10...
Column 0 of A072764, row 0 of A072766, column 1 of A085201. Complement: A081291. Cf. A085223.

Programs

  • Mathematica
    Range[0, Length[#]-1] + CatalanNumber[#] & [Flatten[Array[Table[#, CatalanNumber[#]] &, 7, 0]]] (* Paolo Xausa, Mar 01 2024 *)

Formula

a(n) = n + A000108(A072643(n)) = A069770(A057548(n)) = A080300(A083937(n))

A085201 Array A(x,y): Position of the concatenation of binary strings A014486(x) & A014486(y) in A014486, listed antidiagonalwise as A(0,0), A(1,0), A(0,1), A(2,0), A(1,1), A(0,2), ...

Original entry on oeis.org

0, 1, 1, 2, 2, 2, 3, 4, 4, 3, 4, 6, 9, 5, 4, 5, 9, 14, 10, 9, 5, 6, 11, 23, 15, 23, 10, 6, 7, 14, 28, 24, 37, 24, 11, 7, 8, 16, 37, 29, 65, 38, 25, 12, 8, 9, 19, 42, 38, 79, 66, 39, 26, 13, 9, 10, 23, 51, 43, 107, 80, 67, 40, 27, 23, 10, 11, 25, 65, 52, 121, 108, 81, 68, 41, 65, 24, 11
Offset: 0

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Author

Antti Karttunen, Jun 23 2003

Keywords

Comments

This table is induced by the 2-ary form of the list-function 'append' present in the programming languages like Lisp, Scheme and Prolog.

Crossrefs

Transpose: A085202. Variant: A085203. Row 1: A085223, Column 1: A072795.

Formula

a(0, y)=y, a(x, y) = A072764bi(A072771(x), a(A072772(x), y))
a(x, y) = A080300(A085207bi(A014486(x), A014486(y))) = A085200(A085215bi(A071155(y), A071155(x)))

A080237 Start with 1 and apply the process: k-th run is 1, 2, 3, ..., a(k-1)+1.

Original entry on oeis.org

1, 1, 2, 1, 2, 1, 2, 3, 1, 2, 1, 2, 3, 1, 2, 1, 2, 3, 1, 2, 3, 4, 1, 2, 1, 2, 3, 1, 2, 1, 2, 3, 1, 2, 3, 4, 1, 2, 1, 2, 3, 1, 2, 1, 2, 3, 1, 2, 3, 4, 1, 2, 1, 2, 3, 1, 2, 3, 4, 1, 2, 3, 4, 5, 1, 2, 1, 2, 3, 1, 2, 1, 2, 3, 1, 2, 3, 4, 1, 2, 1, 2, 3, 1, 2, 1, 2
Offset: 1

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Author

Benoit Cloitre, Mar 18 2003

Keywords

Comments

Also a triangle collected from the Catalan generating tree, with row n containing A000108(n) terms and ending with n. Rows converge towards A007001, the "last" row. - Antti Karttunen, Jun 17 2003

Examples

			As an irregular triangle:
  1;
  1,2;
  1,2,1,2,3;
  1,2,1,2,3,1,2,1,2,3,1,2,3,4;
  ...
Sequence begins: 1,(1,2),(1,2),(1,2,3), ... where runs are between 2 parentheses. 5th run is (1,2) since a(4)=1 and sequence continues: 1,1,2,1,2,1,2,3,1,2....
G.f. = x + x^2 + 2*x^3 + x^4 + 2*x^5 + x^6 + 2*x^7 + 3*x^8 + x^9 + 2*x^10 + ...
		

Crossrefs

Cf. A000002, A007001. Positions of ones: A085223. The first occurrence of each n is at A014138(n). See A085178.

Programs

  • Haskell
    a080237 n k = a080237_tabf !! (n-1) !! (k-1)
    a080237_row n = a080237_tabf !! (n-1)
    a080237_tabf = [1] : f a080237_tabf where
       f [[]] =[]
       f (xs:xss) = concatMap (enumFromTo 1 . (+ 1)) xs : f xss
    a080237_list = concat a080237_tabf
    -- Reinhard Zumkeller, Jun 01 2015
  • Mathematica
    run[1] = {1}; run[k_] := run[k] = Range[ Flatten[ Table[run[j], {j, 1, k-1}]][[k-1]] + 1]; Table[run[k], {k, 1, 29}] // Flatten (* Jean-François Alcover, Sep 12 2012 *)
    NestList[ Flatten[# /. # -> Range[# + 1]] &, {1}, 5] // Flatten (* Robert G. Wilson v, Jun 24 2014 *)
  • PARI
    {a(n) = my(v, i, j, k); if( n<1, 0, v=vector(n); for(m=1, n, v[m]=k++; if( k>j, j=v[i++]; k=0)); v[n])}; /* Michael Somos, Jun 24 2014 */
    

Formula

It seems that Sum_{k=1..n} a(k) = C*n*log(log(n)) + O(n*log(log(n))) with C = 0.6....
a(n) = A007814(A014486(n)) (i.e., number of trailing zeros in A063171(n)).

A085178 Array A(x,y) giving the position of the y-th x in A080237 listed by rising antidiagonals.

Original entry on oeis.org

1, 3, 2, 8, 5, 4, 22, 13, 7, 6, 64, 36, 18, 10, 9, 196, 106, 50, 21, 12, 11, 625, 328, 148, 59, 27, 15, 14, 2055, 1054, 460, 176, 63, 32, 17, 16, 6917, 3485, 1483, 550, 190, 78, 35, 20, 19, 23713, 11779, 4915, 1780, 598, 195, 92, 41, 24, 23, 82499, 40509, 16641, 5916
Offset: 1

Views

Author

Antti Karttunen, Jun 18 2003

Keywords

Comments

Read by upwards antidiagonals as A(1,1), A(2,1), A(1,2), A(3,1), A(2,2), A(1,3), etc.

Crossrefs

Transpose: A085176.
Inverse permutation: A085179.
The first row: A014138, the first column: A085223.
Variant: A085180.

A085196 Difference of row 1 and column 1 of the array A085201.

Original entry on oeis.org

0, 0, 0, 1, 0, 1, 3, 4, 6, 0, 1, 3, 4, 6, 9, 10, 12, 13, 15, 18, 19, 21, 24, 0, 1, 3, 4, 6, 9, 10, 12, 13, 15, 18, 19, 21, 24, 28, 29, 31, 32, 34, 37, 38, 40, 41, 43, 46, 47, 49, 52, 56, 57, 59, 60, 62, 65, 66, 68, 71, 75, 76, 78, 81, 85, 0, 1, 3, 4, 6, 9, 10, 12, 13, 15, 18, 19, 21
Offset: 0

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Author

Antti Karttunen, Jun 14 2003

Keywords

Crossrefs

The repeating part: A080336 = A085196 o A081291. Cf. A085197.

Formula

a(n) = A085223(n) - A072795(n).

A085224 A014486-encodings of the plane general trees whose rightmost subtree (branching from the root) is just a stick: /.

Original entry on oeis.org

2, 10, 42, 50, 170, 178, 202, 210, 226, 682, 690, 714, 722, 738, 810, 818, 842, 850, 866, 906, 914, 930, 962, 2730, 2738, 2762, 2770, 2786, 2858, 2866, 2890, 2898, 2914, 2954, 2962, 2978, 3010, 3242, 3250, 3274, 3282, 3298, 3370, 3378, 3402, 3410, 3426, 3466
Offset: 0

Views

Author

Antti Karttunen, Jun 23 2003

Keywords

Formula

a(n) = (4*A014486(n)) + 2 = A014486(A085223(n))

A130374 Signature permutation of a Catalan automorphism: flip the positions of even- and odd-indexed elements at the top level of the list, leaving the last element in place if the length (A057515(n)) is odd.

Original entry on oeis.org

0, 1, 2, 3, 4, 6, 5, 7, 8, 9, 10, 14, 16, 19, 11, 15, 12, 17, 18, 13, 20, 21, 22, 23, 25, 24, 26, 27, 37, 38, 42, 44, 47, 51, 53, 56, 60, 28, 29, 39, 43, 52, 30, 40, 31, 45, 46, 32, 48, 49, 50, 33, 41, 34, 54, 55, 35, 57, 58, 59, 36, 61, 62, 63, 64, 65, 66, 70, 72, 75, 67, 71
Offset: 0

Views

Author

Antti Karttunen, Jun 05 2007

Keywords

Comments

This self-inverse automorphism permutes the top level of a list of even length (1 2 3 4 ... 2n-1 2n) as (2 1 4 3 ... 2n 2n-1), and when applied to a list of odd length (1 2 3 4 ... 2n-1 2n 2n+1), permutes it as (2 1 4 3 ... 2n 2n-1 2n+1).

Crossrefs

Cf. a(n) = A057508(A130373(A057508(n))) = A057164(A130373(A057164(n))) = A127285(A127288(n)) = A127287(A127286(n)). Also a(A085223(n)) = A130370(A122282(A130369(A085223(n)))) holds for all n>=0. The number of cycles and the number of fixed points in range [A014137(n-1)..A014138(n-1)] of this permutation are given by A073193 and A073192.
Showing 1-7 of 7 results.