A265903 -id:A265903 - cp's OEIS frontend

A188163 Smallest m such that A004001(m) = n.

1, 3, 5, 6, 9, 10, 11, 13, 17, 18, 19, 20, 22, 23, 25, 28, 33, 34, 35, 36, 37, 39, 40, 41, 43, 44, 46, 49, 50, 52, 55, 59, 65, 66, 67, 68, 69, 70, 72, 73, 74, 75, 77, 78, 79, 81, 82, 84, 87, 88, 89, 91, 92, 94, 97, 98, 100, 103, 107, 108, 110, 113, 117, 122

Offset: 1

Reinhard Zumkeller, Jun 03 2011

nonn

How is this related to A088359? - R. J. Mathar, Jan 09 2013
It is not hard to show that a(n) exists for all n, and in particular a(n) < 2^n. - Charles R Greathouse IV, Jan 13 2013
From Antti Karttunen, Jan 10 & 18 2016: (Start)
Positions of records in A004001. After 1 the positions where A004001 increases (by necessity by one).
An answer to the question of R. J. Mathar above: This sequence is equal to A088359 with prepended 1. This follows because at each of its unique values (terms of A088359), A004001 must grow, but it can grow nowhere else. See Kubo and Vakil paper and especially the illustrations of Q and R-trees on pages 229-230 (pages 5 & 6 in PDF) and also in sequence A265332.
Obviously A004001 can obtain unique values only at points which form a subset (A266399) of this sequence.
(End)

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
T. Kubo and R. Vakil, On Conway's recursive sequence, Discr. Math. 152 (1996), 225-252.
User "Panurge", Frankl's conjecture and Oeis sequence A188163, Mathoverflow.net, Mar 29 2016.
Eric Weisstein's World of Mathematics, Hofstadter-Conway $10,000 Sequence.
Wikipedia, Hofstadter sequence
Index entries for Hofstadter-type sequences

Equal to A088359 with prepended 1.
Column 1 of A265901, Row 1 of A265903.
Cf. A051135 (first differences).
Cf. A087686 (complement, apart from the initial 1).
Cf. A004001 (also the least monotonic left inverse of this sequence).
Cf. A093879, A265332.
Cf. A266399 (a subsequence).

import Data.List (elemIndex)
import Data.Maybe (fromJust)
a188163 n = succ $ fromJust $ elemIndex n a004001_list

h:=[n le 2 select 1 else Self(Self(n-1)) + Self(n - Self(n-1)): n in [1..500]]; // h=A004001
A188163:= function(n)
   for j in [1..2*n+1] do
       if h[j] eq n then return j; end if;
   end for;
end function;
[A188163(n): n in [1..100]]; // G. C. Greubel, May 20 2024

A188163 := proc(n)
    for a from 1 do
        if A004001(a) = n then
            return a;
        end if;
    end do:
end proc: # R. J. Mathar, May 15 2013

h[1] = 1; h[2] = 1; h[n_] := h[n] = h[h[n-1]] + h[n - h[n-1]];
a[n_] := For[m = 1, True, m++, If[h[m] == n, Return[m]]];
Array[a, 64] (* Jean-François Alcover, Jan 27 2018 *)

@CachedFunction
def h(n): return 1 if (n<3) else h(h(n-1)) + h(n - h(n-1)) # h=A004001
def A188163(n):
    for j in range(1,2*n+2):
        if h(j)==n: return j
[A188163(n) for n in range(1,101)] # G. C. Greubel, May 20 2024

(define A188163 (RECORD-POS 1 1 A004001))
;; Code for A004001 given in that entry. Uses also my IntSeq-library. - Antti Karttunen, Jan 18 2016

Other identities. For all n >= 1:
A004001(a(n)) = n and A004001(m) < n for m < a(n).
A051135(n) = a(n+1) - a(n).

A265901 Square array read by descending antidiagonals: A(n,1) = A188163(n), and for k > 1, A(n,k) = A087686(1+A(n,k-1)).

Original entry on oeis.org

1, 2, 3, 4, 7, 5, 8, 15, 12, 6, 16, 31, 27, 14, 9, 32, 63, 58, 30, 21, 10, 64, 127, 121, 62, 48, 24, 11, 128, 255, 248, 126, 106, 54, 26, 13, 256, 511, 503, 254, 227, 116, 57, 29, 17, 512, 1023, 1014, 510, 475, 242, 120, 61, 38, 18, 1024, 2047, 2037, 1022, 978, 496, 247, 125, 86, 42, 19, 2048, 4095, 4084, 2046, 1992, 1006, 502, 253, 192, 96, 45, 20

Offset: 1

Antti Karttunen, Dec 18 2015

Square array read by descending antidiagonals: A(1,1), A(1,2), A(2,1), A(1,3), A(2,2), A(3,1), etc.
The topmost row (row 1) of the array is A000079 (powers of 2), and in general each row 2^k contains the sequence (2^n - k), starting from the term (2^(k+1) - k). This follows from the properties (3) and (4) of A004001 given on page 227 of Kubo & Vakil paper (page 3 in PDF).
Moreover, each row 2^k - 1 (for k >= 2) contains the sequence 2^n - n - (k-2), starting from the term (2^(k+1) - (2k-1)). To see why this holds, consider the definitions of sequences A162598 and A265332, the latter which also illustrates how the frequency counts Q_n for A004001 are recursively constructed (in the Kubo & Vakil paper).

			The top left corner of the array:
   1,  2,   4,   8,  16,   32,   64,  128,  256,   512,  1024, ...
   3,  7,  15,  31,  63,  127,  255,  511, 1023,  2047,  4095, ...
   5, 12,  27,  58, 121,  248,  503, 1014, 2037,  4084,  8179, ...
   6, 14,  30,  62, 126,  254,  510, 1022, 2046,  4094,  8190, ...
   9, 21,  48, 106, 227,  475,  978, 1992, 4029,  8113, 16292, ...
  10, 24,  54, 116, 242,  496, 1006, 2028, 4074,  8168, 16358, ...
  11, 26,  57, 120, 247,  502, 1013, 2036, 4083,  8178, 16369, ...
  13, 29,  61, 125, 253,  509, 1021, 2045, 4093,  8189, 16381, ...
  17, 38,  86, 192, 419,  894, 1872, 3864, 7893, 16006, 32298, ...
  18, 42,  96, 212, 454,  950, 1956, 3984, 8058, 16226, 32584, ...
  19, 45, 102, 222, 469,  971, 1984, 4020, 8103, 16281, 32650, ...
  20, 47, 105, 226, 474,  977, 1991, 4028, 8112, 16291, 32661, ...
  22, 51, 112, 237, 490,  999, 2020, 4065, 8158, 16347, 32728, ...
  23, 53, 115, 241, 495, 1005, 2027, 4073, 8167, 16357, 32739, ...
  25, 56, 119, 246, 501, 1012, 2035, 4082, 8177, 16368, 32751, ...
  28, 60, 124, 252, 508, 1020, 2044, 4092, 8188, 16380, 32764, ...
  ...

Antti Karttunen, Table of n, a(n) for n = 1..210; the first 20 antidiagonals of array
T. Kubo and R. Vakil, On Conway's recursive sequence, Discr. Math. 152 (1996), 225-252.
Index entries for Hofstadter-type sequences
Index entries for sequences that are permutations of the natural numbers

Inverse permutation: A267102.
Transpose: A265903.
Cf. A265900 (main diagonal).
Cf. A162598 (row index of n in array), A265332 (column index of n in array).
Cf. A004001, A051135, A088359, A087686.
Column 1: A188163.
Column 2: A266109.
Row 1: A000079 (2^n).
Row 2: A000225 (2^n - 1, from 3 onward).
Row 3: A000325 (2^n - n, from 5 onward).
Row 4: A000918 (2^n - 2, from 6 onward).
Row 5: A084634 (?, from 9 onward).
Row 6: A132732 (2^n - 2n + 2, from 10 onward).
Row 7: A000295 (2^n - n - 1, from 11 onward).
Row 8: A036563 (2^n - 3).
Row 9: A084635 (?, from 17 onward).
Row 12: A048492 (?, from 20 onward).
Row 13: A249453 (?, from 22 onward).
Row 14: A183155 (2^n - 2n + 1, from 23 onward. Cf. also A244331).
Row 15: A000247 (2^n - n - 2, from 25 onward).
Row 16: A028399 (2^n - 4).
Cf. also permutations A267111, A267112.

(define (A265901 n) (A265901bi (A002260 n) (A004736 n)))
(define (A265901bi row col) (if (= 1 col) (A188163 row) (A087686 (+ 1 (A265901bi row (- col 1))))))

For the first column k=1, A(n,1) = A188163(n), for columns k > 1, A(n,k) = A087686(1+A(n,k-1)).

A267112 Permutation of natural numbers: a(1) = 1; a(2n) = A087686(1+a(n)), a(2n+1) = A088359(a(n)), where A088359 and A087686 = numbers that occur only once (resp. more than once) in A004001.

Original entry on oeis.org

1, 2, 3, 4, 5, 7, 6, 8, 9, 12, 10, 15, 13, 14, 11, 16, 17, 21, 18, 27, 22, 24, 19, 31, 28, 29, 23, 30, 25, 26, 20, 32, 33, 38, 34, 48, 39, 42, 35, 58, 49, 51, 40, 54, 43, 45, 36, 63, 59, 60, 50, 61, 52, 53, 41, 62, 55, 56, 44, 57, 46, 47, 37, 64, 65, 71, 66, 86, 72, 76, 67, 106, 87, 90, 73, 96, 77, 80, 68, 121, 107, 109, 88

Offset: 1

Antti Karttunen, Jan 10 2016

This sequence can be represented as a binary tree. Each left hand child is produced as A087686(1+n), and each right hand child as A088359(n), when their parent contains n:
                                    |
                 ...................1...................
                2                                       3
      4......../ \........5                   7......../ \........6
     / \                 / \                 / \                 / \
    /   \               /   \               /   \               /   \
   /     \             /     \             /     \             /     \
  8       9          12       10         15       13         14       11
16 17   21 18      27  22   24  19     31  28   29  23     30  25   26  20
etc.
The level k of the tree contains all numbers of binary width k, like many base-2 related permutations (A003188, A054429, etc). For a proof, see A267110, which gives the contents of each parent node (for node containing n).
A276442 shows the mirror-image of the same tree.

Antti Karttunen, Table of n, a(n) for n = 1..8192
T. Kubo and R. Vakil, On Conway's recursive sequence, Discr. Math. 152 (1996), 225-252.
Index entries for Hofstadter-type sequences
Index entries for sequences that are permutations of the natural numbers

Inverse: A267111.
Cf. A000079, A000225, A004001, A006127, A087686, A088359, A267110.
Similar or related permutations: A003188, A054429, A276442, A233276, A233278, A276344, A276346, A276446.
Cf. also permutations A266411, A266412 and arrays A265901, A265903.

a(1) = 1; after which, a(2n) = A087686(1+a(n)), a(2n+1) = A088359(a(n)).
As a composition of other permutations:
a(n) = A276442(A054429(n)).
a(n) = A276344(A233276(n)).
a(n) = A276346(A233278(n)).
a(n) = A276446(A003188(n)).
Other identities. For all n >= 0:
a(2^n) = 2^n. [Follows from the properties (3) and (4) of A004001 given on page 227 of Kubo & Vakil paper.]
a(A000225(n)) = A006127(n), i.e., a((2^(n+1)) - 1) = 2^n + n. [Numbers at the right edge.]

A162598 Ordinal transform of A265332.

Original entry on oeis.org

1, 1, 2, 1, 3, 4, 2, 1, 5, 6, 7, 3, 8, 4, 2, 1, 9, 10, 11, 12, 5, 13, 14, 6, 15, 7, 3, 16, 8, 4, 2, 1, 17, 18, 19, 20, 21, 9, 22, 23, 24, 10, 25, 26, 11, 27, 12, 5, 28, 29, 13, 30, 14, 6, 31, 15, 7, 3, 32, 16, 8, 4, 2, 1, 33, 34, 35, 36, 37, 38, 17, 39, 40, 41, 42, 18, 43, 44, 45, 19, 46, 47

Offset: 1

Franklin T. Adams-Watters, Jul 07 2009

This is a fractal sequence.
It appears that each group of 2^k terms starts with 1 and ends with the remaining powers of two from 2^k down to 2^1.
From Antti Karttunen, Jan 09-12 2016: (Start)
This is ordinal transform of A265332, which is modified A051135 (with a(1) = 1, instead of 2). -  after Franklin T. Adams-Watters' original definition for this sequence.
A000079 (powers of 2) indeed gives the positions of ones in this sequence. This follows from the properties (3) and (4) of A004001 given on page 227 of Kubo & Vakil paper (page 3 of PDF), which together also imply the pattern observed above, more clearly represented as:
a(2) = 1.
a(3..4) = 2, 1.
a(6..8) = 4, 2, 1.
a(13..16) = 8, 4, 2, 1.
a(28..31) = 16, 8, 4, 2, 1.
etc.
(End)

Antti Karttunen, Table of n, a(n) for n = 1..8192
T. Kubo and R. Vakil, On Conway's recursive sequence, Discr. Math. 152 (1996), 225-252.
Index entries for Hofstadter-type sequences

Cf. A004001, A051135, A080677, A087686.
Row index of A265901, column index of A265903.
Cf. A265332 (corresponding other index).
Cf. A000079 (positions of ones).
Cf. A000225 (from the term 3 onward the positions of 2's).
Cf. A000325 (from its third term 5 onward the positions of 3's, which occur always as the last term before the next descending subsequence of powers of two).

terms = 100;
h[1] = 1; h[2] = 1;
h[n_] := h[n] = h[h[n - 1]] + h[n - h[n - 1]];
t = Array[h, 2*terms];
A051135 = Take[Transpose[Tally[t]][[2]], terms];
b[_] = 1;
a[n_] := a[n] = With[{t = If[n == 1, 1, A051135[[n]]]}, b[t]++];
Array[a, terms] (* Jean-François Alcover, Dec 19 2021, after Robert G. Wilson v in A051135 *)

Let b(1) = 1, b(n) = A051135(n) for n > 1. Then a(n) is the number of b(k) that equal b(n) for 1 <= k <= n: sum( 1, 1<=k<=n and a(k)=a(n) ).

If A265332(n) = 1, then a(n) = A004001(n), otherwise a(n) = a(A080677(n)-1) = a(n - A004001(n)). - Antti Karttunen, Jan 09 2016

Name amended by Antti Karttunen, Jan 09 2016

A276441 Permutation of natural numbers: a(1) = 1, a(A087686(1+n)) = 1 + 2a(n), a(A088359(n)) = 2a(n), where A088359 & A087686 = numbers that occur only once & more than once in A004001.

Original entry on oeis.org

1, 3, 2, 7, 6, 4, 5, 15, 14, 12, 8, 13, 10, 9, 11, 31, 30, 28, 24, 16, 29, 26, 20, 25, 18, 17, 27, 22, 21, 19, 23, 63, 62, 60, 56, 48, 32, 61, 58, 52, 40, 57, 50, 36, 49, 34, 33, 59, 54, 44, 53, 42, 41, 51, 38, 37, 35, 55, 46, 45, 43, 39, 47, 127, 126, 124, 120, 112, 96, 64, 125, 122, 116, 104, 80, 121, 114, 100, 72, 113, 98

Offset: 1

Antti Karttunen, Sep 03 2016

Antti Karttunen, Table of n, a(n) for n = 1..8191
T. Kubo and R. Vakil, On Conway's recursive sequence, Discr. Math. 152 (1996), 225-252.
Index entries for sequences related to binary expansion of n
Index entries for Hofstadter-type sequences
Index entries for sequences that are permutations of the natural numbers

Inverse: A276442.
Cf. A000079, A000225, A004001, A080677, A087686, A088359, A093879.
Related or similar permutations: A006068, A054429, A233275, A233277, A267111, A276343, A276345, A276443.
Cf. also arrays A265901, A265903.

(definec (A276441 n) (cond ((< n 2) n) ((zero? (A093879 (- n 1))) (+ 1 (* 2 (A276441 (+ -1 (A080677 n)))))) (else (* 2 (A276441 (+ -1 (A004001 n)))))))

a(1) = 1; for n > 1, if A093879(n-1) = 0 [when n is in A087686], a(n) = 1 + 2*a(A080677(n)-1), otherwise [when n is in A088359], a(n) = 2*a(A004001(n)-1).
As a composition of other permutations:
a(n) = A054429(A267111(n)).
a(n) = A233277(A276343(n)).
a(n) = A233275(A276345(n)).
a(n) = A006068(A276443(n)).
Other identities. For all n >= 1:
a(A000079(n-1)) = A000225(n).

A266411 a(1) = 1, after which each a(n) = (A004074(n)+1)-th number selected from those not yet in the sequence.

Original entry on oeis.org

1, 2, 4, 3, 6, 8, 7, 5, 10, 12, 14, 13, 16, 15, 11, 9, 18, 20, 22, 24, 23, 26, 28, 27, 30, 29, 25, 32, 31, 21, 19, 17, 34, 36, 38, 40, 42, 41, 44, 46, 48, 47, 50, 52, 51, 54, 53, 49, 56, 58, 57, 60, 59, 55, 62, 61, 45, 43, 64, 63, 39, 37, 35, 33, 66, 68, 70, 72, 74, 76, 75, 78, 80, 82, 84, 83, 86, 88, 90, 89, 92, 94, 93, 96, 95, 91

Offset: 1

Antti Karttunen, Dec 29 2015

nonn

Inverse: A266412.
Cf. A004074.
Similar permutations in Quetian style: A119435, A126917, A246165, A266413.
Cf. also A265901, A265903.

f[n_] := Block[{a = {1}, g, b = Range[2, n]}, g[1] = g[2] = 1; g[x_] := g[x] = g[g[x - 1]] + g[x - g[x - 1]]; Do[{AppendTo[a, #[[1, 1]]], Set[b, Last@ #]} &@ If[# > Length@ b, Break[], TakeDrop[b, {#}]] &@ (2 g[#] - # + 1) &@ k, {k, 2, n}]; a]; f@ 97 (* Michael De Vlieger, Dec 29 2015, Version 10.2, based on Harvey P. Dale at A004074 *)

cp's OEIS Frontend

A188163 Smallest m such that A004001(m) = n.

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A265901 Square array read by descending antidiagonals: A(n,1) = A188163(n), and for k > 1, A(n,k) = A087686(1+A(n,k-1)).

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A267112 Permutation of natural numbers: a(1) = 1; a(2n) = A087686(1+a(n)), a(2n+1) = A088359(a(n)), where A088359 and A087686 = numbers that occur only once (resp. more than once) in A004001.

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A162598 Ordinal transform of A265332.

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A276441 Permutation of natural numbers: a(1) = 1, a(A087686(1+n)) = 1 + 2*a(n), a(A088359(n)) = 2*a(n), where A088359 & A087686 = numbers that occur only once & more than once in A004001.

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A266411 a(1) = 1, after which each a(n) = (A004074(n)+1)-th number selected from those not yet in the sequence.

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A276441 Permutation of natural numbers: a(1) = 1, a(A087686(1+n)) = 1 + 2a(n), a(A088359(n)) = 2a(n), where A088359 & A087686 = numbers that occur only once & more than once in A004001.