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.

A096104 Digit reversal of A096299(n).

Original entry on oeis.org

1, 11, 21, 111, 211, 221, 321, 1111, 2111, 2211, 3211, 2221, 3221, 3321, 4321, 11111, 21111, 22111, 32111, 22211, 32211, 33211, 43211, 22221, 32221, 33221
Offset: 1

Views

Author

Amarnath Murthy, Jun 26 2004

Keywords

Comments

First occurrence of n is the most significant digit of a(2^n-1).

Crossrefs

Cf. A096299.

A095684 Triangle read by rows. There are 2^(m-1) rows of length m, for m = 1, 2, 3, ... The rows are in lexicographic order. The rows have the property that the first entry is 1, the second distinct entry (reading from left to right) is 2, the third distinct entry is 3, etc.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 2, 1, 2, 3, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 2, 3, 1, 2, 2, 2, 1, 2, 2, 3, 1, 2, 3, 3, 1, 2, 3, 4, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 1, 2, 3, 1, 1, 2, 2, 2, 1, 1, 2, 2, 3, 1, 1, 2, 3, 3, 1, 1, 2, 3, 4, 1, 2, 2, 2, 2, 1, 2, 2, 2, 3, 1, 2, 2, 3, 3
Offset: 1

Views

Author

N. J. A. Sloane, Jun 25 2004

Keywords

Comments

Row k is the unique multiset that covers an initial interval of positive integers and has multiplicities equal to the parts of the k-th composition in standard order (graded reverse-lexicographic, A066099). This composition is obtained by taking the set of positions of 1's in the reversed binary expansion of k, prepending 0, taking first differences, and reversing again. For example, the 13th composition is (1,2,1), so row 13 is {1,2,2,3}. - Gus Wiseman, Apr 26 2020

Examples

			1, 11, 12, 111, 112, 122, 123, 1111, 1112, 1122, 1123, 1222, 1223, 1233, ...
The 8 strings of length 4 are 1111, 1112, 1122, 1123, 1222, 1223, 1233, 1234.
From _Gus Wiseman_, Apr 26 2020: (Start)
The triangle read by columns begins:
  1:{1}  2:{1,1}  4:{1,1,1}   8:{1,1,1,1}  16:{1,1,1,1,1}
         3:{1,2}  5:{1,1,2}   9:{1,1,1,2}  17:{1,1,1,1,2}
                  6:{1,2,2}  10:{1,1,2,2}  18:{1,1,1,2,2}
                  7:{1,2,3}  11:{1,1,2,3}  19:{1,1,1,2,3}
                             12:{1,2,2,2}  20:{1,1,2,2,2}
                             13:{1,2,2,3}  21:{1,1,2,2,3}
                             14:{1,2,3,3}  22:{1,1,2,3,3}
                             15:{1,2,3,4}  23:{1,1,2,3,4}
                                           24:{1,2,2,2,2}
                                           25:{1,2,2,2,3}
                                           26:{1,2,2,3,3}
                                           27:{1,2,2,3,4}
                                           28:{1,2,3,3,3}
                                           29:{1,2,3,3,4}
                                           30:{1,2,3,4,4}
                                           31:{1,2,3,4,5}
(End)
		

Crossrefs

See A096299 for another version.
The number of distinct parts in row n is A000120(n), also the maximum part.
Row sums are A029931.
Heinz numbers of rows are A057335.
Row lengths are A070939.
Row products are A284001.
The version for prime indices is A305936.
There are A333942(n) multiset partitions of row n.
Multisets of compositions are counted by A034691.
Combinatory separations of normal multisets are A269134.
All of the following pertain to compositions in standard order (A066099):
- Necklaces are A065609.
- Strict compositions are A233564.
- Constant compositions are A272919.
- Lyndon words are A275692.
- Dealings are counted by A333939.
- Distinct parts are counted by A334028.

Programs

  • Mathematica
    stc[n_]:=Differences[Prepend[Join@@Position[Reverse[IntegerDigits[n,2]],1],0]]//Reverse;
    ptnToNorm[y_]:=Join@@Table[ConstantArray[i,y[[i]]],{i,Length[y]}];
    Table[ptnToNorm[stc[n]],{n,15}] (* Gus Wiseman, Apr 26 2020 *)

A110382 Numbers which are sum of distinct unary numbers (containing only ones), i.e., numbers which are sum of distinct numbers of the form (10^k - 1)/9.

Original entry on oeis.org

1, 11, 12, 111, 112, 122, 123, 1111, 1112, 1122, 1123, 1222, 1223, 1233, 1234, 11111, 11112, 11122, 11123, 11222, 11223, 11233, 11234, 12222, 12223, 12233, 12234, 12333, 12334, 12344, 12345, 111111, 111112, 111122, 111123, 111222, 111223
Offset: 1

Views

Author

Amarnath Murthy, Jul 25 2005

Keywords

Comments

Not the same as A096299, since a(1023) = 1234567900 which is not in lexicographic order. - Ralf Stephan, May 17 2007

Crossrefs

Cf. A096299.

Programs

  • Maple
    f:= proc(n) local L,i:
      L:= convert(n,base,2);
      add(L[i]*(10^i-1)/9, i=1..nops(L))
    end proc:
    map(f, [$1..100]); # Robert Israel, Feb 03 2025
  • Mathematica
    Nest[Append[#1, 10 #1[[Floor[#2/2] ]] + DigitCount[#2, 2, 1]] & @@ {#, Length[#] + 1} &, {1}, 36] (* Michael De Vlieger, Mar 12 2021 *)
  • PARI
    a(n) = sum(k=0, log(n)\log(2), hammingweight(n\(2^k))*10^k); \\ Michel Marcus, May 09 2019
    
  • PARI
    a(n) = my(b = Vecrev(binary(n))); sum(i = 1, #b, b[i] * (10^i-1)) / 9 \\ David A. Corneth, May 19 2019

Formula

G.f.: 1/(1-x) * Sum_{k>=0} (10^(k+1) - 1)/9 * x^2^k/(1 + x^2^k). - Ralf Stephan, May 17 2007
a(n) = 10*a(floor(n/2)) + A000120(n) = Sum_{k=0..floor(log_2(n))} A000120(floor(n/(2^k)))*10^k. - Mikhail Kurkov, May 08 2019
a(n) = a(floor(n/2)) + A007088(n) = (10*A007088(n) - A000120(n))/9. - Mikhail Kurkov, Mar 03 2021

Extensions

a(1024) ff. corrected by Georg Fischer, Feb 03 2025
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