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 1-4 of 4 results.

A214414 Fixed points of permutations A105027 and A214417.

Original entry on oeis.org

0, 1, 5, 7, 18, 22, 26, 30, 1031, 1039, 1047, 1055, 1063, 1071, 1079, 1087, 1095, 1103, 1111, 1119, 1127, 1135, 1143, 1151, 1159, 1167, 1175, 1183, 1191, 1199, 1207, 1215, 1223, 1231, 1239, 1247, 1255, 1263, 1271, 1279, 1287, 1295, 1303, 1311, 1319, 1327
Offset: 1

Views

Author

Reinhard Zumkeller, Jul 21 2012

Keywords

Comments

A105027(a(n)) = A214417(a(n)) = a(n).

Crossrefs

Programs

  • Haskell
    a214414 n = a214414_list !! (n-1)
    a214414_list = [x | x <- [0..], a105027 x == x]

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

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

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)
Showing 1-4 of 4 results.