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A257798 Permutation of natural numbers: a(1) = 1; a(2n) = nontriangular(a(n)), a(2n+1) = triangular(1+a(n)), where triangular = A000217, nontriangular = A014132. 3
1, 2, 3, 4, 6, 5, 10, 7, 15, 9, 28, 8, 21, 14, 66, 11, 36, 20, 136, 13, 55, 35, 435, 12, 45, 27, 253, 19, 120, 77, 2278, 16, 78, 44, 703, 26, 231, 152, 9453, 18, 105, 65, 1596, 43, 666, 464, 95266, 17, 91, 54, 1081, 34, 406, 275, 32385, 25, 210, 135, 7381, 89, 3081, 2345, 2598060, 22, 153, 90, 3160, 53, 1035, 740, 248160, 33 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This sequence can be represented as a binary tree. Each left hand child is produced as A014132(n) and each right hand child as A000217(1+n), when a parent contains n >= 1:

                                    1

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

                2                                       3

      4......../ \........6                   5......../ \.......10

     / \                 / \                 / \                 / \

    /   \               /   \               /   \               /   \

   /     \             /     \             /     \             /     \

  7       15          9       28          8       21         14       66

11 36   20  136     13 55   35  435     12 45   27  253    19  120  77 2278

etc.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..1024

Index entries for sequences that are permutations of the natural numbers

FORMULA

a(1)=1; after which: a(2n) = A014132(a(n)), a(2n+1) = A000217(a(n)+1).

PROG

(Scheme, with memoizing definec-macro)

(definec (A257798 n) (cond ((<= n 1) n) ((even? n) (A014132 (A257798 (/ n 2)))) (else (A000217 (+ 1 (A257798 (/ (- n 1) 2)))))))

CROSSREFS

Inverse: A257797.

Cf. A000217, A014132.

Cf. also permutation A183079.

Sequence in context: A064275 A080998 A209268 * A183079 A119629 A014631

Adjacent sequences:  A257795 A257796 A257797 * A257799 A257800 A257801

KEYWORD

nonn

AUTHOR

Antti Karttunen, May 18 2015

STATUS

approved

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Last modified September 20 06:27 EDT 2021. Contains 347577 sequences. (Running on oeis4.)