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 14 results. Next

A161919 Permutation of natural numbers: concatenation of subsequences A161924(A000070(k-1)..A026905(k)), k >= 1, each sorted into ascending order.

Original entry on oeis.org

1, 2, 3, 4, 5, 7, 6, 8, 9, 11, 15, 10, 13, 16, 17, 19, 23, 31, 12, 14, 18, 21, 27, 32, 33, 35, 39, 47, 63, 20, 22, 25, 29, 34, 37, 43, 55, 64, 65, 67, 71, 79, 95, 127, 24, 26, 30, 36, 38, 41, 45, 51, 59, 66, 69, 75, 87, 111, 128, 129, 131, 135, 143, 159, 191, 255, 28, 40
Offset: 1

Views

Author

Alford Arnold, Jun 23 2009

Keywords

Comments

This is the lexicographically earliest sequence a_n for which it holds that A161511(a(n)) = A036042(n) for all n.
Triangle T(n,k) read by rows. Row n lists in increasing order the viabin numbers of the integer partitions of n (n >= 1, k >= 1). The viabin number of an integer partition is defined in the following way. Consider the southeast border of the Ferrers board of the integer partition and consider the binary number obtained by replacing each east step with 1 and each north step, except the last one, with 0. The corresponding decimal form is, by definition, the viabin number of the given integer partition. "Viabin" is coined from "via binary". For example, consider the integer partition [3,1,1] of 5. The southeast border of its Ferrers board yields 10011, leading to the viabin number 19 (an entry in the 5th row). - Emeric Deutsch, Sep 06 2017
After specifying the value of n, the first Maple program yields the entries of row n. - Emeric Deutsch, Feb 26 2016
After specifying the value of m, the third Maple program yields the first m rows; the command partovi(p) yields the viabin number of the partition p = [a,b,c,...]. - Emeric Deutsch, Aug 31 2017

Examples

			This can be viewed as an irregular table, where row r (>= 1) has A000041(r) elements, i.e., as 1; 2,3; 4,5,7; 6,8,9,11,15; 10,13,16,17,19,23,31; etc. A125106 illustrates how each number is mapped to a partition.
		

Crossrefs

Inverse: A166277. Sequence A161924 gives the same rows before sorting.

Programs

  • Maple
    n := 11: s := proc (b) local t, i, j: t := 0: for i to nops(b) do for j from i+1 to nops(b) do if b[j]-b[i] = 1 then t := t+1 else  end if end do end do: t end proc: A[n] := {}: for i to 2^n do a[i] := convert(2*i, base, 2) end do: for k to 2^n do if s(a[k]) = n then A[n] := `union`(A[n], {k}) else  end if end do: A[n]; # Emeric Deutsch, Feb 26 2016
    # second Maple program:
    f:= proc(l) local i, r; r:= 0; for i to nops(l)-1 do
           r:= 2*((x-> 2*x+1)@@(l[i+1]-l[i]))(r) od; r/2
        end:
    b:= proc(n, i) `if`(n=0 or i=1, [[0, 1$n]], [b(n, i-1)[],
          `if`(i>n, [], map(x-> [x[], i], b(n-i, i)))[]])
        end:
    T:= n-> sort(map(f, b(n$2)))[]:
    seq(T(n), n=1..10);  # Alois P. Heinz, Jul 25 2017
    # 3rd Maple program:
    m := 10; with(combinat): ff := proc (X) local s: s := [1, seq(0, j = 1 .. X[2])]: s := map(convert, s, string): return cat(op(s)) end proc: partovi := proc (P) local X, n, Y, i: X := convert(P, multiset): n := X[-1][1]: Y := map(proc (t) options operator, arrow: t[1] end proc, X): for i to n do if member(i, Y) = false then X := [op(X), [i, 0]] end if end do: X := sort(X, proc (s, t) options operator, arrow: evalb(s[1] < t[1]) end proc): X := map(ff, X): X := cat(op(X)): n := parse(X): n := convert(n, decimal, binary): (1/2)*n end proc: for n to m do {seq(partovi(partition(n)[q]), q = 1 .. numbpart(n))} end do; # Emeric Deutsch, Aug 31 2017
  • Mathematica
    columns = 10;
    row[n_] := n - 2^Floor[Log2[n]];
    col[0] = 0; col[n_] := If[EvenQ[n], col[n/2] + DigitCount[n/2, 2, 1], col[(n-1)/2] + 1];
    Clear[T]; T[, ] = 0; Do[T[row[k], col[k]] = k, {k, 1, 2^columns}];
    Table[DeleteCases[Sort @ Table[T[n-1, k], {n, 1, 2^(k-1)}], 0], {k, 1, columns}] // Flatten (* Jean-François Alcover, Feb 16 2021 *)

Extensions

Edited and extended by Antti Karttunen, Oct 12 2009

A167979 Linearize the arrays A099627 A124922 ... defined in A167204 and based on A161924 then concatenate to form a new table.

Original entry on oeis.org

1, 2, 6, 3, 10, 12, 4, 13, 20, 14, 5, 18, 25, 22, 24, 7, 21, 36, 29, 40, 26, 8, 27, 41, 38, 49, 42, 28, 9, 34, 51, 45, 72, 53, 44, 30, 11, 37, 68, 59, 81, 74, 57, 46, 48, 15, 43, 73, 70, 99, 85, 76, 61, 80, 50, 16, 55, 83, 77, 136, 107, 89, 78, 97, 82, 52
Offset: 1

Views

Author

Alford Arnold, Nov 15 2009

Keywords

Comments

Contribution from Alford Arnold, Nov 29 2009: (Start)
Note that the values within A167977 identify the number partitioned described in A125106 and A161924.
(End)

Examples

			The resulting table begins:
..1..2..3..4..5..7..8
..6.10.13.18.21.27
.12.20.25.36.41
.14.22.29.38
etc.
Contribution from _Alford Arnold_, Nov 29 2009: 4 equals 2+2 which maps to the natural number 6 (binary 110) and 6 appears in the second array (A124922).
		

Crossrefs

Contribution from Alford Arnold, Nov 29 2009: (Start)
A125106(Describes the mapping to partitions). A167977 is A161511(A167979).
(End)

Extensions

Corrected By Alford Arnold, Nov 29 2009

A166276 Inverse permutation to A161924.

Original entry on oeis.org

1, 2, 3, 4, 5, 9, 6, 7, 8, 14, 10, 23, 16, 25, 11, 12, 13, 21, 15, 34, 24, 36, 17, 53, 38, 55, 27, 79, 40, 58, 18, 19, 20, 32, 22, 49, 35, 51, 26, 75, 54, 77, 39, 109, 57, 81, 28, 113, 83, 115, 60, 159, 85, 118, 42, 219, 120, 164, 62, 223, 88, 123, 29, 30, 31, 47, 33, 71
Offset: 1

Views

Author

Antti Karttunen, Oct 12 2009

Keywords

Crossrefs

Inverse: A161924. Cf. A166277.

A171426 Row sum of column n in A126441 or A161924.

Original entry on oeis.org

1, 5, 16, 49, 129, 341, 833, 2029, 4760, 11068, 25182, 56888, 126661, 280169, 613893, 1337386, 2893793, 6232013, 13352607, 28497552, 60580905, 128368080, 271153740, 571224871, 1200298631, 2516483260, 5264785310, 10993631034, 22915508186, 47688470005
Offset: 1

Views

Author

Alford Arnold, Dec 12 2009

Keywords

Comments

From Emeric Deutsch, Sep 06 2017: (Start)
Row sums of the triangle A161919.
a(n) = sum of the viabin numbers of the partitions of n. The viabin number of an integer partition is defined in the following way. Consider the southeast border of the Ferrers board of the integer partition and consider the binary number obtained by replacing each east step with 1 and each north step, except the last one, with 0. The corresponding decimal form is, by definition, the viabin number of the given integer partition. "Viabin" is coined from "via binary". For example, consider the integer partition [3,1,1] of 5. The southeast border of its Ferrers board yields 10011, leading to the viabin number 19. (End)

Examples

			The values 8,9,6,11,15 map to 1111,211,22,31,4, respectively; so a(4) = 8+9+6+11+15 = 49.
		

Crossrefs

Programs

  • Maple
    with(combinat): a := proc (n) local ff, partovi: ff := proc (X) local s: s := [1, seq(0, j = 1 .. X[2])]: s := map(convert, s, string): return cat(op(s)) end proc: partovi := proc (P) local X, n, Y, i: X := convert(P, multiset): n := X[-1][1]: Y := map(proc (t) options operator, arrow: t[1] end proc, X): for i to n do if member(i, Y) = false then X := [op(X), [i, 0]] end if end do: X := sort(X, proc (s, t) options operator, arrow: evalb(s[1] < t[1]) end proc): X := map(ff, X); X := cat(op(X)): n := parse(X): n := convert(n, decimal, binary): (1/2)*n end proc: add(partovi(partition(n)[j]), j = 1 .. numbpart(n)) end proc: seq(a(n), n = 1 .. 27); # the subprogram partovi (due to W. Edwin Clark) yields the viabin number of a given partition. # Emeric Deutsch, Sep 06 2017
    # second Maple program:
    b:= proc(n, i, l, r) option remember; `if`(n=0, r, `if`(i>n, 0,
          b(n, i+1, l, r)+b(n-i, i$2, ((x-> 2*x+1)@@(i-l))(2*r))))
        end:
    a:= n-> b(n, 1, 0$2):
    seq(a(n), n=1..30);  # Alois P. Heinz, Mar 01 2021
  • Mathematica
    b[n_, i_, l_, r_] := b[n, i, l, r] = If[n == 0, r, If[i>n, 0,
         b[n, i+1, l, r] + b[n-i, i, i, Nest[2#+1&, 2r, i-l]]]];
    a[n_] := b[n, 1, 0, 0];
    Array[a, 30] (* Jean-François Alcover, Mar 02 2021, after Alois P. Heinz *)

Extensions

Ninth term corrected by Alford Arnold, Jan 22 2010
Offset changed to 1 and a(17)-a(27) from Emeric Deutsch, Sep 06 2017
a(28)-a(30) from Alois P. Heinz, Sep 07 2017

A171429 Irregular table of positive integers with the property that each term on row r can be mapped to a numeric partition conjugate to the partition mapped by the corresponding value within sequence A161924.

Original entry on oeis.org

1, 3, 2, 7, 5, 4, 15, 11, 6, 9, 8, 31, 23, 13, 19, 10, 17, 16, 63, 47, 27, 39, 14, 21, 12, 35, 18, 33, 32, 127, 95, 55, 79, 29, 43, 25, 71, 22, 37, 20, 67, 34, 65, 64, 255, 191, 111, 159, 59, 87, 51, 143, 30, 45, 26, 75, 41, 24, 135, 38, 69, 36, 131, 66, 129, 128, 511, 383, 223
Offset: 1

Views

Author

Alford Arnold, Dec 08 2009, Dec 10 2009

Keywords

Comments

This appears to be a sorted version of sequence A059894.

Examples

			a(29) = 20 and a(20) = 29, forming a pair of numbers mapping to partitions 4+3=7 and 2+2+2+1=7.
The table has shape A000041 and begins
   1;
   3  2;
   7  5  4;
  15 11  6  9  8;
  ...
		

Crossrefs

A167200 Multiply the A161924 by 4 then add 2.

Original entry on oeis.org

6, 10, 14, 18, 2, 30, 34, 38, 26, 46, 62, 66, 70, 42, 78, 54, 94, 126, 130, 134, 74, 142, 50, 86, 58, 158, 110, 190, 254
Offset: 1

Views

Author

Alford Arnold, Oct 30 2009

Keywords

Examples

			a(n) begins 6 10 14 18 22 30 34 38 26 46 62 ...
because A161924 begins:
1.2.4..8.16.32.64.128.256.512.1024
..3.5..9.17.33.65.129.257.513.1025
.......6.10.18.34..66.130.258..514
....7.11.19.35.67.131.259.515.1027
............12.20..36..68.132..260
.........13.21.37..69.133.261..517
............14.22..38..70.134..262
......15.23.39.71.135.263.519.1031
...................24..40..72..136
...............25..41..73.137..265
...................26..42..74..138
............27.43..75.139.267..523
.......................28..44...76
...............29..45..77.141..269
...................30..46..78..142
.........31.47.79.143.271.527.1039
...........................48...80
.......................49..81..145
...........................50...82
...................51..83.147..275
		

Crossrefs

A126441 Tabular arrangement of the natural numbers: the row on which any nonzero term a(n) appears in is A053645(a(n))=A053645(n+1), and the column is A161511(a(n)). Table is presented by columns with 2^{k-1} items in column k, unused positions are filled with 0's.

Original entry on oeis.org

1, 2, 3, 4, 5, 0, 7, 8, 9, 6, 11, 0, 0, 0, 15, 16, 17, 10, 19, 0, 13, 0, 23, 0, 0, 0, 0, 0, 0, 0, 31, 32, 33, 18, 35, 12, 21, 14, 39, 0, 0, 0, 27, 0, 0, 0, 47, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 63, 64, 65, 34, 67, 20, 37, 22, 71, 0, 25, 0, 43, 0, 29, 0, 79, 0, 0, 0, 0, 0, 0, 0, 55, 0, 0
Offset: 0

Views

Author

Alford Arnold, Jan 19 2007

Keywords

Comments

Note: 1 might be a more natural starting offset for this sequence, although the identities concerning A053645 and A161511 would have to be changed. - Antti Karttunen, Oct 12 2009.
This can be regarded as an arrangement of the partitions, indexed by position in A125106. The partitions in a given row all have the same remaining partition when the largest part is removed; specifically, the partition indexed by the row number in A125106 (with row 0 having the empty partition remaining).
The first value on row n is A004760(n+1). The second value on each row is A004760(n+1) plus A062383(n); subsequent values increase by ever enlarging powers of two. Or equivalently, each subsequent value on the row after the first nonzero value is given by A004754(previous value on the same row).
A055941(r) tells how many terms the row r (>= 0) has been shifted rightward from its "natural position", i.e. with how many zeros that row has been prepended.
The number of (nonzero) entries in column k is A000041(k).

Examples

			The largest power of 2 <= 6 is 4, 6 - 4 = 2, so 6 is in row 2. By A125106, 6 corresponds to the partition [2^2], total 4, so 6 goes in column 4. Thus T(2,4) = 6.
The table begins:
1.2.4..8.16.32.64.128.256.512.1024
..3.5..9.17.33.65.129.257.513.1025
.......6.10.18.34..66.130.258..514
....7.11.19.35.67.131.259.515.1027
............12.20..36..68.132..260
.........13.21.37..69.133.261..517
............14.22..38..70.134..262
......15.23.39.71.135.263.519.1031
...................24..40..72..136
...............25..41..73.137..265
...................26..42..74..138
............27.43..75.139.267..523
.......................28..44...76
...............29..45..77.141..269
...................30..46..78..142
.........31.47.79.143.271.527.1039
...........................48...80
.......................49..81..145
...........................50...82
...................51..83.147..275
		

Crossrefs

Cf. A125106, A053645, A000041, A004760, A062383, A000079 (column lengths).
A053645(a(A166274(n))) = A053645(1+A166274(n)) for all n>=1.
Positions of zeros: A166275, this sequence without zeros: A161924. A161920(n) gives the position of the first nonzero term on the row n-1.

Programs

  • Mathematica
    columns = 7; row[n_] := n-2^Floor[Log2[n]]; col[0] = 0; col[n_] := If[EvenQ[n], col[n/2] + DigitCount[n/2, 2, 1], col[(n-1)/2]+1]; Clear[T]; T[, ] = 0; Do[T[row[k], col[k]] = k, {k, 1, 2^columns}]; Table[T[n-1, k], {k, 1, columns}, {n, 1, 2^(k-1)}] // Flatten (* Jean-François Alcover, Sep 09 2017 *)

Extensions

Edited by Franklin T. Adams-Watters, Jan 23 2007
Further edited and Scheme-code added by Antti Karttunen, Oct 12 2009

A124922 Second in a series of triangular arrays providing index numbers for subsequences of A060351.

Original entry on oeis.org

6, 10, 13, 18, 21, 27, 34, 37, 43, 55, 66, 69, 75, 87, 111, 130, 133, 139, 151, 175, 223
Offset: 1

Views

Author

Alford Arnold, Nov 21 2006

Keywords

Comments

The first triangular array is A099627 which provides index numbers in A060351 for Pascal's Triangle (A007318). This second array provides the index numbers in A060351 for array A059797.
Note that this table and A099627 are sub-arrays of table A161924 which has A000041 entries per row. - Alford Arnold, Oct 19 2009

Examples

			A060351(34,37,43,55) = (14,35,35,14) = Row Four of Array A059797.
		

Crossrefs

Extensions

I would like a clearer definition of this and other recent triangles from this author. - N. J. A. Sloane, Nov 22 2006
More terms from Alford Arnold, Oct 19 2009

A166274 Positions of nonzero terms in A126441.

Original entry on oeis.org

0, 1, 2, 3, 4, 6, 7, 8, 9, 10, 14, 15, 16, 17, 18, 20, 22, 30, 31, 32, 33, 34, 35, 36, 37, 38, 42, 46, 62, 63, 64, 65, 66, 67, 68, 69, 70, 72, 74, 76, 78, 86, 94, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 140, 141, 142, 146, 150, 154, 158, 174
Offset: 1

Views

Author

Antti Karttunen, Oct 12 2009

Keywords

Comments

Here we assume that the starting offset of A126441 is 0, i.e., A126441(0)=1, A126441(1)=2, etc.

Crossrefs

Complement: A166275. See A161924.

A167201 Third in a series of triangular subarrays of A117506. Previous arrays are Tables A007318 and A059797.

Original entry on oeis.org

5, 14, 21, 28, 70, 56, 48, 162, 216, 120
Offset: 1

Views

Author

Alford Arnold, Nov 02 2009

Keywords

Comments

This subarray is generated from values related to the source partition 3+3. (cf A161924).

Examples

			The domain values begin:
12
20..25
36..41..51
68..73..83..103
so based on function A117506, a(n) begins:
5
14..21
28..70..56
48..162..216..120
Note that A117506(22) maps to Partition 3+3
which corresponds to the 12th natural number appearing in A161924.
		

Crossrefs

Showing 1-10 of 14 results. Next