A279967 -id:A279967 - cp's OEIS frontend

A281533 Numbers such that A279967(n) = 0.

17, 23, 47, 57, 93, 107, 155, 173, 233, 255, 327, 353, 437, 467, 563, 597, 677, 705, 743, 863, 905, 1037, 1083, 1187, 1227, 1277, 1433, 1487, 1607, 1655, 1713, 1893, 1955, 2027, 2095, 2147, 2213, 2293, 2357, 2417, 2467, 2487, 2503, 2703, 2719, 2777, 2861, 2993, 3005, 3083, 3251

Offset: 1

Hartmut F. W. Hoft, Jan 23 2017

nonn

This sequence is neither a subset nor a superset of sequence A278436 since 155 and 817 are in one, but not the other, respectively.

			Number 155 = 5*31, equivalent to array position (17, 2), is in the sequence since all prior numbers in column 1 are even as are those in column 2, except 9 which is not a factor of 155.

Cf. A278436, A279966, A279967.

(* support functions are in A279967*)
a281533[k_] := Module[{ut=upperTriangle[k], ms=Table[" ", {i, 1, k}, {j, 1, k}], h, pos, val, seqL={}}, ms[[1, 1]]=1; For[h=2, h<=Length[ut], h++, pos=ut[[h]]; val=Apply[Plus, Select[Map[ms[[Apply[Sequence, #]]]&, priorPos[pos]], #!=0 && Mod[seqPos[pos], #]==0&]]; If[val==0,AppendTo[seqL, val]]; ms[[Apply[Sequence, pos]]]=val]; seqL]
a281533[81] (* data *)

A279212 Fill an array by antidiagonals upwards; in the top left cell enter a(0)=1; thereafter, in the n-th cell, enter the sum of the entries of those earlier cells that can be seen from that cell.

Original entry on oeis.org

1, 1, 2, 2, 6, 11, 4, 15, 39, 72, 8, 37, 119, 293, 543, 16, 88, 330, 976, 2364, 4403, 32, 204, 870, 2944, 8373, 20072, 37527, 64, 464, 2209, 8334, 26683, 74150, 176609, 331072, 128, 1040, 5454, 22579, 79534, 246035, 673156, 1595909, 2997466, 256, 2304, 13176, 59185, 226106, 762221, 2303159, 6231191, 14721429, 27690124

Offset: 0

N. J. A. Sloane, Dec 24 2016

"That can be seen from" means "that are on the same row, column, diagonal, or antidiagonal as".
Inspired by A279967.
Conjecture: Every column has a finite number of odd entries, and every row and diagonal have an infinite number of odd entries. - Peter Kagey, Mar 28 2020. The conjecture about columns is true, see that attached pdf file from Alec Jones.
The "look" keyword refers to Peter Kagey's bitmap. - N. J. A. Sloane, Mar 29 2020
The number of sequences of queen moves from (1, 1) to (n, k) in the first quadrant moving only up, right, diagonally up-right, or diagonally up-left. - Peter Kagey, Apr 12 2020
Column 0 gives A011782. In the column 1, the only powers of 2 occur at positions A233328(k) with value a(k(k+1)/2 + 1), k >=1 (see A335903). Conjecture: Those are the only multiple occurrences of numbers greater than 1 in this sequence (checked through the first 2000 antidiagonals). - Hartmut F. W. Hoft, Jun 29 2020

			The array begins:
i/j|  0    1    2     3     4      5      6       7       8
-------------------------------------------------------------
0  |  1    2   11    72   543   4403  37527  331072 2997466 ...
1  |  1    6   39   293  2364  20072 176609 1595909 ...
2  |  2   15  119   976  8373  74150 673156 ...
3  |  4   37  330  2944 26683 246035 ...
4  |  8   88  870  8334 79534 ...
5  | 16  204 2209 22579 ...
6  | 32  464 5454 ...
7  | 64 1040 ...
8  |128 ...
  ...
For example, when we get to the antidiagonal that reads 4, 15, 39, ..., the reason for the 39 is that from that cell we can see one cell that has been filled in above it (containing 11), one cell to the northwest (2), two cells to the west (1, 6), and two to the southwest (4, 15), for a total of a(8) = 39.
The next pair of duplicates greater than 2 is 2^20 = 1048576 = a(154) = a(231), located in antidiagonals 17 = A233328(2) and 21, respectively. For additional duplicate numbers in this sequence see A335903.  - _Hartmut F. W. Hoft_, Jun 29 2020

Alois P. Heinz, Antidiagonals n = 0..200, flattened (first 20 antidiagonals from Alec Jones)
Alec Jones, Proof that columns have finitely many odd entries.
Peter Kagey, Bitmap showing parity of first 1024 rows and 512 columns. (Odd values are white; even values are black.)
Peter Kagey, Animated example illustrating the first fifteen terms.

Cf. A064642 is analogous if a cell can only "see" its immediate neighbors.
Cf. A035002, A059450, A132439, A279966, A279967, A279211.
See A280026, A280027 for similar sequences based on a spiral.
Cf. A011782, A335903.

s[0, 0] = 1; s[i_, j_] := s[i, j] = Sum[s[k, j], {k, 0, i-1}] + Sum[s[i, k], {k, 0, j-1}] + Sum[s[i+j-k, k], {k, 0, j-1}] + Sum[s[i-k-1, j-k-1], {k, 0, Min[i, j] - 1}]
aDiag[m_] := Map[s[m-#, #]&, Range[0, m]]
a279212[n_] := Flatten[Map[aDiag, Range[0, n]]]
a279212[9] (* data - 10 antidiagonals;  Hartmut F. W. Hoft, Jun 29 2020 *)

T(0, 0) = 1; T(i, j) = Sum_{k=0..i-1} T(k, j) + Sum_{k=0..j-1} T(i, k) + Sum_{k=0..j-1} T(i+j-k, k) + Sum_{k=0..min(i, j)-1} T(i-k-1, j-k-1), with recursion upwards along antidiagonals. - Hartmut F. W. Hoft, Jun 29 2020

A279966 Square array read by antidiagonals upwards in which each term is the number of prior elements in the same row, column, diagonal, or antidiagonal that divide n; the array is seeded with an initial value a(1)=1.

Original entry on oeis.org

1, 1, 2, 2, 2, 4, 2, 5, 1, 5, 2, 5, 2, 5, 4, 5, 0, 4, 1, 9, 2, 5, 0, 6, 6, 3, 4, 6, 2, 7, 1, 6, 4, 6, 5, 11, 2, 4, 2, 10, 1, 8, 2, 10, 3, 7, 0, 9, 4, 6, 3, 5, 1, 9, 5, 8, 0, 5, 1, 14, 4, 4, 2, 10, 7, 8, 2, 4, 2, 11, 3, 16, 3, 6, 7, 8, 5, 10

Offset: 1

Alec Jones, Dec 24 2016

The patterns of values 2 and 0 in columns 1 and 2, respectively, of the triangle of sequence A279967 do not hold for this sequence, in addition, it appears that every column contains two 1's. - Hartmut F. W. Hoft, Jan 23 2017

			After the first 21 terms, the array looks like this:
1  2  4  5  4  2
1  2  1  5  9
2  5  2  1
2  5  4
2  0
5
...
We have a(20) = 9 because 20 is divisible by a(2) = 1, a(5) = 2, a(9) = 1, a(10) = 5, a(14) = 5, a(15) = 4, a(16) = 5, a(18) = 4, and a(19) = 1.
Likewise, a(17) = 0 because no prior elements of the same row, column, diagonal, or antidiagonal divide 17. See A278436 for a list of indices for which a(n) = 0.
From _Hartmut F. W. Hoft_, Jan 23 2017: (Start)
Expanded triangle to the first 13 antidiagonals  (as in A279967)
.
1   2   4   5   4   2   6  11   3   5   8  10   1
1   2   1   5   9   4   5  10   9   7   5  18
2   5   2   1   3   6   2   1  10   8   2
2   5   4   6   4   8   5   2   7  10
2   0   6   6   1   3   4   6   3
5   0   1  10   6   4   3   5
5   7   2   4  14  16   5
2   4   9   1   3  16
2   0   5  11   2
7   0   2   4
8   4   4
2   9
2
(End)

Peter Kagey, Table of n, a(n) for n = 1..5000

Cf. A279967 for the related sequence which sums prior terms.
Cf. A278436.
Cf. A281533. - Hartmut F. W. Hoft, Jan 23 2017

(* printing of the triangle is commented out of function a279966[] *)
(* support functions are in A279967 *)
a279966[k_] := Module[{ut=upperTriangle[k], ms=Table[" ", {i, 1, k}, {j, 1, k}], h, pos, val, seqL={1}}, ms[[1, 1]]=1; For[h=2, h<=Length[ut], h++, pos=ut[[h]]; val=Length[Select[Map[ms[[Apply[Sequence, #]]]&, priorPos[pos]], #!=0 && Mod[seqPos[pos], #]==0&]]; AppendTo[seqL, val]; ms[[Apply[Sequence, pos]]]=val]; (* Print[TableForm[ms]]; *) seqL]
a279966[13] (* values in first 13 antidiagonals. *)
(* Hartmut F. W. Hoft, Jan 23 2017 *)

Appended name with phrase as in A279967. - Hartmut F. W. Hoft, Jan 23 2017

A279211 Fill an array by antidiagonals upwards; in the n-th cell, enter the number of earlier cells that can be seen from that cell.

Original entry on oeis.org

0, 1, 2, 2, 4, 4, 3, 5, 6, 6, 4, 6, 8, 8, 8, 5, 7, 9, 10, 10, 10, 6, 8, 10, 12, 12, 12, 12, 7, 9, 11, 13, 14, 14, 14, 14, 8, 10, 12, 14, 16, 16, 16, 16, 16, 9, 11, 13, 15, 17, 18, 18, 18, 18, 18, 10, 12, 14, 16, 18, 20, 20, 20, 20, 20, 20, 11, 13, 15, 17

Offset: 0

N. J. A. Sloane, Dec 24 2016

"That can be seen from" means "that are on the same row, column, diagonal, or antidiagonal as".
Inspired by A279967.
Since the sum of row and column index is constant for elements in an antidiagonal, the entries along an antidiagonal on and above the diagonal equal twice the number of the antidiagonal. - Hartmut F. W. Hoft, Jun 29 2020

			The array begins:
x\y| 0  1  2  3  4  5  6 ...
---+--------------------
  0| 0  2  4  6  8 10 12 ...
  1| 1  4  6  8 10 12 ...
  2| 2  5  8 10 12 ...
  3| 3  6  9 12 ...
  4| 4  7 10 13 ...
  5| 5  8 11 14 ...
  6| ...
...
For example, when we get to the antidiagonal that reads 4, 6, 8 ..., the reason for the 8 is that from that cell we can see two cells that have been filled in above it (containing 4 and 6), two cells to the northwest (0, 4), two cells to the west (2, 5), and two to the southwest (4, 6), which is 8 cells, so a(12) = 8.

Alec Jones, Table of n, a(n) for n = 0..5049

Cf. A279966, A279967, A279212.

See A280026, A280027 for similar sequences based on a spiral.

countCells[i_, j_] := i + 2*j + Min[i, j]
a279211[m_] := Map[countCells[m - #, #]&, Range[0, m]]
Flatten[Map[a279211,Range[0,10]]]  (* antidiagonals 0..10 data - Hartmut F. W. Hoft, Jun 29 2020 *)

T(x,y) = x+3*y if x >= y; T(x,y) = 2*(x+y) if x <= y.

T(i, j) = i + 2*j + min(i, j). - Hartmut F. W. Hoft, Jun 29 2020

More terms from Alec Jones, Dec 25 2016

A278436 Numbers such that A279966(n) = 0.

Original entry on oeis.org

17, 23, 47, 57, 93, 107, 173, 233, 353, 437, 467, 563, 677, 743, 817, 829, 851, 863, 955, 1037, 1187, 1213, 1277, 1387, 1433, 1487, 1549, 2089, 2147, 2213, 2287, 2293, 2417, 2473, 2689, 2777, 2911, 3083, 3323, 3391, 6691, 9337, 22969, 38557, 47347, 75391, 104999, 130927, 146719

Offset: 1

Alec Jones, Dec 24 2016

nonn

Not all numbers in this list are prime; nonprime elements include 57, 93, 437, 817, 851, 955, 1037, 1387, 2147.

This sequence is neither a subset nor a superset of sequence A281533 since 155 and 817 are the first numbers in one, but not the other, respectively. - Hartmut F. W. Hoft, Jan 23 2017

			Number 817 = 19*43, equivalent to array position (4, 37), is in the sequence since none of the numbers in the prior column, diagonal, row and antidiagonal contain the counts of 1, 19, 43 and 817. - _Hartmut F. W. Hoft_, Jan 23 2017

Cf. A279966, A000124, A145018, A152948, A152950, A167499, A279967.

(* support functions are in A279967 *)
a278436[k_] := Module[{ut=upperTriangle[k], ms=Table[" ", {i, 1, k}, {j, 1, k}], h, pos, val, seqL={}}, ms[[1, 1]]=1; For[h=2, h<=Length[ut], h++, pos=ut[[h]]; val=Length[Select[Map[ms[[Apply[Sequence, #]]]&, priorPos[pos]], #!=0 && Mod[seqPos[pos], #]==0&]]; If[val==0, AppendTo[seqL, h]]; ms[[Apply[Sequence, pos]]]=val]; seqL]
a278436[100] (* data through 3391. - Hartmut F. W. Hoft, Jan 23 2017 *)

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A281533 Numbers such that A279967(n) = 0.

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A279212 Fill an array by antidiagonals upwards; in the top left cell enter a(0)=1; thereafter, in the n-th cell, enter the sum of the entries of those earlier cells that can be seen from that cell.

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A279966 Square array read by antidiagonals upwards in which each term is the number of prior elements in the same row, column, diagonal, or antidiagonal that divide n; the array is seeded with an initial value a(1)=1.

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A279211 Fill an array by antidiagonals upwards; in the n-th cell, enter the number of earlier cells that can be seen from that cell.

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A278436 Numbers such that A279966(n) = 0.

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