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 1-10 of 11 results. Next

A105271 Fixed points of the permutation of the nonnegative integers defined by A105025 (i.e., n such that A105025(n) = n).

Original entry on oeis.org

0, 1, 4, 6, 17, 21, 25, 29, 1024, 1032, 1040, 1048, 1056, 1064, 1072, 1080, 1088, 1096, 1104, 1112, 1120, 1128, 1136, 1144, 1152, 1160, 1168, 1176, 1184, 1192, 1200, 1208, 1216, 1224, 1232, 1240, 1248, 1256, 1264, 1272, 1280, 1288, 1296, 1304, 1312, 1320
Offset: 1

Views

Author

Emeric Deutsch, Apr 16 2005

Keywords

Crossrefs

Programs

  • Haskell
    a105271 n = a105271_list !! (n-1)
    a105271_list = [x | x <- [0..], a105025 x == x]
    -- Reinhard Zumkeller, Jul 21 2012

Extensions

More terms from John W. Layman, Jun 03 2005
Offset corrected by Reinhard Zumkeller, Jul 21 2012

A214433 Where A105025 and A105027 agree.

Original entry on oeis.org

0, 1, 2, 3, 9, 10, 13, 14, 34, 37, 42, 45, 50, 53, 58, 61, 517, 522, 533, 538, 549, 554, 565, 570, 581, 586, 597, 602, 613, 618, 629, 634, 645, 650, 661, 666, 677, 682, 693, 698, 709, 714, 725, 730, 741, 746, 757, 762, 773, 778, 789, 794, 805, 810, 821, 826
Offset: 1

Views

Author

Reinhard Zumkeller, Jul 21 2012

Keywords

Comments

A105025(a(n)) = A105027(a(n)).

Examples

			A105025(1018) = A105027(1018) = 1011, => 1018 is a term: a(80) = 1018;
A105025(1019) = 994 and A105027(1019) = 1014, => 1019 not a term;
A105025(524302) = A105027(524302) = 524317, => a(81) = 524302;
A105025(524303) = 524312 and A105027(524303) = 524300, => 524302 not a term.
-
		

Crossrefs

Cf. A214489.

Programs

  • Haskell
    a214433 n = a214433_list !! (n-1)
    a214433_list = [x | x <- [0..], a105025 x == a105027 x]

A105026 Binary equivalents of A105025.

Original entry on oeis.org

0, 1, 11, 10, 100, 111, 110, 101, 1011, 1010, 1001, 1100, 1111, 1110, 1101, 1000, 10010, 10001, 10100, 10111, 10110, 10101, 10000, 11011, 11010, 11001, 11100, 11111, 11110, 11101, 11000, 10011, 100001, 100100, 100111, 100110, 100101
Offset: 0

Views

Author

N. J. A. Sloane, Apr 03 2005

Keywords

Crossrefs

Formula

a(n) = A007088(A105025(n)). - Michel Marcus, May 06 2020

Extensions

More terms from Emeric Deutsch, Apr 16 2005

A214416 Inverse permutation to A105025.

Original entry on oeis.org

0, 1, 3, 2, 4, 7, 6, 5, 15, 10, 9, 8, 11, 14, 13, 12, 22, 17, 16, 31, 18, 21, 20, 19, 30, 25, 24, 23, 26, 29, 28, 27, 37, 32, 63, 46, 33, 36, 35, 34, 45, 40, 39, 38, 41, 44, 43, 42, 53, 48, 47, 62, 49, 52, 51, 50, 61, 56, 55, 54, 57, 60, 59, 58, 68, 127, 94
Offset: 0

Views

Author

Reinhard Zumkeller, Jul 21 2012

Keywords

Crossrefs

Cf. A214417, A105271 (fixed points).

Programs

  • Haskell
    import Data.List (elemIndex)
    import Data.Maybe (fromJust)
    a214416 = fromJust . (`elemIndex` a105025_list)

A105153 Consider trajectory of n under repeated application of map k -> A105025(k); a(n) = length of cycle.

Original entry on oeis.org

1, 1, 2, 2, 1, 2, 1, 2, 4, 2, 2, 4, 4, 2, 2, 4, 4, 1, 4, 4, 4, 1, 4, 4, 4, 1, 4, 4, 4, 1, 4, 4, 4, 4, 8, 4, 4, 4, 4, 8, 4, 4, 8, 4, 4, 4, 4, 8, 4, 4, 8, 4, 4, 4, 4, 8, 4, 4, 8, 4, 4, 4, 4, 8, 2, 16, 8, 4, 2, 4, 8, 16, 2, 16, 8, 4, 2, 4, 8, 16, 2, 16, 8, 4, 2, 4, 8, 16, 2, 16, 8, 4, 2, 4, 8, 16, 2, 16, 8, 4, 2
Offset: 0

Views

Author

Philippe Deléham, Apr 30 2005

Keywords

Comments

Why is this always a power of 2?

Crossrefs

Positions of 1's: A105271.

Programs

  • Haskell
    a105153 n = t [n] where
       t xs@(x:_) | y `elem` xs = length xs
                  | otherwise   = t (y : xs) where y = a105025 x
    -- Reinhard Zumkeller, Jul 21 2012

Extensions

More terms from R. J. Mathar, Aug 10 2007

A102370 "Sloping binary numbers": write numbers in binary under each other (right-justified), read diagonals in upward direction, convert to decimal.

Original entry on oeis.org

0, 3, 6, 5, 4, 15, 10, 9, 8, 11, 14, 13, 28, 23, 18, 17, 16, 19, 22, 21, 20, 31, 26, 25, 24, 27, 30, 61, 44, 39, 34, 33, 32, 35, 38, 37, 36, 47, 42, 41, 40, 43, 46, 45, 60, 55, 50, 49, 48, 51, 54, 53, 52, 63, 58, 57, 56, 59, 126, 93, 76, 71, 66, 65, 64, 67, 70, 69
Offset: 0

Views

Author

Philippe Deléham, Feb 13 2005

Keywords

Comments

All terms are distinct, but certain terms (see A102371) are missing. But see A103122.
Trajectory of 1 is 1, 3, 5, 15, 17, 19, 21, 31, 33, ..., see A103192.

Examples

			........0
........1
.......10
.......11
......100
......101
......110
......111
.....1000
.........
The upward-sloping diagonals are:
0
11
110
101
100
1111
1010
.......
giving 0, 3, 6, 5, 4, 15, 10, ...
The sequence has a natural decomposition into blocks (see the paper): 0; 3; 6, 5, 4; 15, 10, 9, 8, 11, 14, 13; 28, 23, 18, 17, 16, 19, 22, 21, 20, 31, 26, 25, 24, 27, 30; 61, ...
Reading the array of binary numbers along diagonals with slope 1 gives this sequence, slope 2 gives A105085, slope 0 gives A001477 and slope -1 gives A105033.
		

Crossrefs

Related sequences (1): A103542 (binary version), A102371 (complement), A103185, A103528, A103529, A103530, A103318, A034797, A103543, A103581, A103582, A103583.
Related sequences (2): A103584, A103585, A103586, A103587, A103127, A103192 (trajectory of 1), A103122, A103588, A103589, A103202 (sorted), A103205 (base 10 version).
Related sequences (3): A103747 (trajectory of 2), A103621, A103745, A103615, A103842, A103863, A104234, A104235, A103813, A105023, A105024, A105025, A105026, A105027, A105028.
Related sequences (4): A105029, A105030, A105031, A105032, A105033, A105034, A105035, A105108.

Programs

  • Haskell
    a102370 n = a102370_list !! n
    a102370_list = 0 : map (a105027 . toInteger) a062289_list
    -- Reinhard Zumkeller, Jul 21 2012
    
  • Maple
    A102370:=proc(n) local t1,l; t1:=n; for l from 1 to n do if n+l mod 2^l = 0 then t1:=t1+2^l; fi; od: t1; end;
  • Mathematica
    f[n_] := Block[{k = 1, s = 0, l = Max[2, Floor[Log[2, n + 1] + 2]]}, While[k < l, If[ Mod[n + k, 2^k] == 0, s = s + 2^k]; k++ ]; s]; Table[ f[n] + n, {n, 0, 71}] (* Robert G. Wilson v, Mar 21 2005 *)
  • PARI
    A102370(n)=n-1+sum(k=0,ceil(log(n+1)/log(2)),if((n+k)%2^k,0,2^k)) \\ Benoit Cloitre, Mar 20 2005
    
  • PARI
    {a(n) = if( n<1, 0, sum( k=0, length( binary( n)), bitand( n + k, 2^k)))} /* Michael Somos, Mar 26 2012 */
    
  • Python
    def a(n): return 0 if n<1 else sum([(n + k)&(2**k) for k in range(len(bin(n)[2:]) + 1)]) # Indranil Ghosh, May 03 2017

Formula

a(n) = n + Sum_{ k >= 1 such that n + k == 0 mod 2^k } 2^k. (Cf. A103185.) In particular, a(n) >= n. - N. J. A. Sloane, Mar 18 2005
a(n) = A105027(A062289(n)) for n > 0. - Reinhard Zumkeller, Jul 21 2012

Extensions

More terms from Benoit Cloitre, Mar 20 2005

A105027 Write numbers in binary under each other; to get the next block of 2^k (k >= 0) terms of the sequence, start at 2^k, read diagonals in upward direction and convert to decimal.

Original entry on oeis.org

0, 1, 3, 2, 6, 5, 4, 7, 15, 10, 9, 8, 11, 14, 13, 12, 28, 23, 18, 17, 16, 19, 22, 21, 20, 31, 26, 25, 24, 27, 30, 29, 61, 44, 39, 34, 33, 32, 35, 38, 37, 36, 47, 42, 41, 40, 43, 46, 45, 60, 55, 50, 49, 48, 51, 54, 53, 52, 63, 58, 57, 56, 59, 62, 126, 93, 76, 71, 66, 65, 64, 67, 70
Offset: 0

Views

Author

N. J. A. Sloane, Apr 03 2005

Keywords

Comments

This is a permutation of the nonnegative integers.
Structure: blocks of size 2^k - 1 taken from A102370, interspersed with terms of A102371. - Philippe Deléham, Nov 17 2007
a(A062289(n)) = A102370(n) for n > 0; a(A000225(n)) = A102371(n); a(A214433(n)) = A105025(a(n)). - Reinhard Zumkeller, Jul 21 2012

Examples

			        0
        1
       10
       11
   -> 100  Starting here, the upward diagonals
      101  read 110, 101, 100, 111, giving the block 6, 5, 4, 7.
      110
      111
     1000
     1001
     1010
     1011
      ...
		

Crossrefs

Cf. A214414 (fixed points), A214417 (inverse).

Programs

  • Haskell
    import Data.Bits ((.|.), (.&.))
    a105027 n = foldl (.|.) 0 $ zipWith (.&.)
                      a000079_list $ enumFromTo (n + 1 - a070939 n) n
    -- Reinhard Zumkeller, Jul 21 2012
    
  • Mathematica
    block[k_] := Module[{t}, t = Table[PadLeft[IntegerDigits[n, 2], k+1], {n, 2^(k-1), 2^(k+1)-1}]; Table[FromDigits[Table[t[[n-m+1, m]], {m, 1, k+1}], 2], {n,2^(k-1)+1, 2^(k-1)+2^k}]]; block[0] = {0, 1}; Table[block[k], {k, 0, 6}] // Flatten (* Jean-François Alcover, Jun 30 2015 *)
  • PARI
    apply( {A105027(n,L=exponent(n+!n))=sum(k=0,L,bitand(n+k-L,2^k))}, [0..55]) \\ M. F. Hasler, Apr 18 2022

Formula

a(2^n - 1) = A102371(n) for n > 0. - Philippe Deléham, May 10 2005

Extensions

More terms from John W. Layman, Apr 07 2005

A105033 Read binary numbers downwards to the right.

Original entry on oeis.org

0, 1, 0, 3, 2, 1, 4, 7, 6, 5, 0, 11, 10, 9, 12, 15, 14, 13, 8, 3, 18, 17, 20, 23, 22, 21, 16, 27, 26, 25, 28, 31, 30, 29, 24, 19, 2, 33, 36, 39, 38, 37, 32, 43, 42, 41, 44, 47, 46, 45, 40, 35, 50, 49, 52, 55, 54, 53, 48, 59, 58, 57, 60, 63, 62, 61, 56, 51, 34, 1, 68, 71, 70, 69, 64, 75
Offset: 0

Views

Author

N. J. A. Sloane, Apr 04 2005

Keywords

Comments

Equals A103530(n+2) - 1. - Philippe Deléham, Apr 06 2005
This sequence can also be produced as follows:
Using binary arithmetic, start with zero and repeatedly add 1 while deferring carries one iteration.
a(0) = 0, c(0) = 1
a(n) = a(n-1) XOR c(n-1)
c(n) = (a(n-1) AND c(n-1))*2+1
where c is the carries, XOR is bitwise exclusive-or, and AND is bitwise and.
This has the property that a(n) = n-c(n)+1. - Christopher Scussel, Jan 31 2025

Examples

			Start with the binary numbers:
  ......0
  ......1
  .....10
  .....11
  ....100
  ....101
  ....110
  ....111
  ...1000
  .......
and read downwards to the right, getting 0, 1, 0, 11, 10, 1, 100, 111, ...
		

Crossrefs

Analog of A102370. Cf. A105034, A105025.
Cf. triangular array in A103589.

Programs

  • Maple
    f:= proc (n) local t1, l; t1 := n; for l from 0 to n do if `mod`(n-l,2^(l+1)) = 0 and n >= 2^(l+1) then t1 := t1-2^(l+1) fi; od; t1; end proc;
  • Mathematica
    f[n_] := Block[{k = 0, s = 0}, While[2^(k + 1) < n + 1, If[ Mod[n, 2^(k + 1)] == k, s = s + 2^(k + 1)]; k++ ]; n - s]; Table[ f[n], {n, 0, 75}] (* Robert G. Wilson v, Apr 06 2005 *)

Formula

a(n) = n - Sum_{ k >= 0, 2^{k+1} <= n, n == k mod 2^(k+1) } 2^(k+1).
Structure: blocks of size 2^k taken from A105025, interspersed with terms a(n) itself! Thus a(2^k + k - 1 ) = a(k-1) for k >= 1.
From David Applegate, Apr 06 2005: (Start)
"a(n) = 2^k + a(n-2^k) if k >= 1 and 0 <= n - 2^k - k < 2^k, = a(n-2^k) if k >= 1 and n - 2^k - k = -1, or = 0 if n = 0 (and exactly one of the three conditions is true for any n >= 0).
"Equivalently, a(2^k + k + x) = 2^k + a(k+x) if 0 <= x < 2^k, = a(k+x) if x = -1 (for each n >= 0, there is a unique k, x such that 2^k + k + x = n, k >= 0, -1 <= x < 2^k). This recurrence follows immediately from the definition.
"The recurrence captures three observed facts about a: a(2^k + k - 1) = a(k-1); a consists of blocks of length 2^k of A105025 interspersed with terms of a; a(n) = n - Sum_{ k >= 0, 2^{k+1} <= n, n = k mod 2^(k+1) } 2^(k+1)." (End)
a(n) = sum_{k=0..n} A103589(n,k)*2^(n-k). - L. Edson Jeffery, Dec 01 2013

A214489 Numbers m such that A070939(m) = A070939(m + A070939(m)), A070939 = length of binary representation.

Original entry on oeis.org

0, 4, 8, 9, 10, 11, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86
Offset: 1

Views

Author

Reinhard Zumkeller, Jul 21 2012

Keywords

Comments

A070939(a(n))=A103586(a(n)) and also A105025(a(n))=A105029(a(n)).

Programs

  • Haskell
    a214489 n = a214489_list !! (n-1)
    a214489_list = [x | x <- [0..], a070939 x == a103586 x]
    -- .

A105029 Write numbers in binary under each other, left justified, read diagonals in downward direction, convert to decimal.

Original entry on oeis.org

0, 2, 6, 5, 4, 14, 13, 8, 11, 10, 9, 12, 30, 29, 24, 19, 18, 17, 20, 23, 22, 21, 16, 27, 26, 25, 28, 62, 61, 56, 51, 34, 33, 36, 39, 38, 37, 32, 43, 42, 41, 44, 47, 46, 45, 40, 35, 50, 49, 52, 55, 54, 53, 48, 59, 58, 57, 60, 126, 125, 120, 115, 98, 65, 68, 71, 70
Offset: 0

Views

Author

Benoit Cloitre, Apr 03 2005

Keywords

Comments

All terms are distinct, but the numbers 2^m - 1 are missing.
a(n) = Sum_{k>=1} B(n+k-1,k)*2^(A103586(n)-k) where B(n,k) n>=1, k>=1 is the infinite array:
1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,...
1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,...
1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,...
1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,...
1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,...
1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,...
1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,...
1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,...
1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,...
.......
where n-th row consists of binary expansion of n followed by 0's.
a(n) = A105025(n) iff A070939(n) = A103586(n), cf. A214489. - Reinhard Zumkeller, Jul 21 2012

Examples

			0
1
1 0
1 1
1 0 0
1 0 1
1 1 0
1 1 1
1 0 0 0
1 0 0 1
1 0 1 0
and reading the diagonals downwards we get 0, 10, 110, 101, 100, 1110, 1101, etc.
		

Crossrefs

Programs

  • Haskell
    import Data.Bits ((.|.), (.&.))
    a105029 n = foldl (.|.) 0 $ zipWith (.&.) a000079_list $
       map (\x -> (len + 1 - a070939 x) * x)
           (reverse $ enumFromTo n (n - 1 + len))  where len = a103586 n
    -- Reinhard Zumkeller, Jul 21 2012
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