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 1-3 of 3 results.

A119589 Natural numbers from 1 to 100 sorted lexicographically.

Original entry on oeis.org

1, 10, 100, 11, 12, 13, 14, 15, 16, 17, 18, 19, 2, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 3, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 4, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 5, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 6, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 7, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 8, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 9, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99
Offset: 1

Views

Author

Dmitry Kamenetsky, Jun 01 2006, Jun 03 2006

Keywords

Examples

			a(1) = 1.
a(2) = 10 because "10" > "1".
a(3) = 100 because "100" > "10", but "100" < "11".
		

Crossrefs

Cf. A119590 (inverse permutation: position of n in this sequence).
Cf. A190016, A190017 (integers 1..10^4 in lexicographical order, and inverse).

Programs

  • PARI
    A119589=vecsort(vector(100,n,Str(n)),,1) \\ M. F. Hasler, Sep 03 2018, edited Oct 25 2019
    
  • PARI
    a(n)=if(n<4, 10^n\10, n=divrem(n+8, 11); n[2]<10, [10,1]*n, n[1]+1) \\ M. F. Hasler, Oct 26 2019

Formula

a(n) = if n < 4 then 10^(n-1) else if r < 10 then 10*q + r else q + 1, where [q,r] are the base-11 digits of n+8. - M. F. Hasler, Oct 26 2019

A190017 Inverse permutation to A190016: lexicographical ordering of integers 1 .. 10^4.

Original entry on oeis.org

1, 1113, 2224, 3335, 4446, 5557, 6668, 7779, 8890, 2, 114, 225, 336, 447, 558, 669, 780, 891, 1002, 1114, 1225, 1336, 1447, 1558, 1669, 1780, 1891, 2002, 2113, 2225, 2336, 2447, 2558, 2669, 2780, 2891, 3002, 3113, 3224, 3336, 3447, 3558, 3669, 3780, 3891
Offset: 1

Views

Author

Reinhard Zumkeller, May 06 2011

Keywords

Comments

a(A190016(n)) = A190016(a(n)) = n.

Crossrefs

Cf. A190016 (inverse: integers 1..10^4 in lexicographical order).
Cf. A119589, A119590 (integers 1..100 in lexicographical order, and inverse).

Programs

  • Haskell
    import Data.List (elemIndex)
    import Data.Maybe (fromJust)
    a190017 n = a190017_list !! (n-1)
    a190017_list =
       map (succ . fromJust . (`elemIndex` a190016_list)) [1..10000]
    
  • PARI
    A190017=vecsort(A190016=vecsort(vector(10^4,n,Str(n)),,1),,1) \\ M. F. Hasler, Oct 26 2019

A309590 Inverse of A309589: 0-based positions in the number subsets {0, ..., 10^k - 1} written in base 10 and sorted lexicographically, for k = 1, 2, ...

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 12, 23, 34, 45, 56, 67, 78, 89, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55
Offset: 0

Views

Author

Georg Fischer, Mar 02 2019

Keywords

Comments

The sequence is related to the flattened form of the irregular table T(k, i) described in A309589. There, the rows for k >= 1 contain a permutation of the numbers 0 <= i <= 10^k - 1 which is defined by the lexicographical order of the numbers i written in base 10.
The sequence here lists, per sorted row k, the 0-based positions of the numbers i in that row. The positions in row k are also a permutation of the numbers 0 <= i <= 10^k - 1.

Crossrefs

Cf. A119590 (like row k=2, but i = 1..100), A190017 (like row k=4, but for i = 1..10000), A309589.

Programs

  • Perl
    # cf. link
Showing 1-3 of 3 results.