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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.

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A354373 Square spiral on a 2D square lattice, one term per cell, starting at the origin with 0; the digits of the four integers forming any 2 X 2 square add up to a prime.

Original entry on oeis.org

0, 1, 2, 4, 3, 6, 5, 8, 11, 7, 9, 10, 12, 14, 15, 13, 16, 18, 23, 21, 17, 25, 27, 19, 22, 20, 24, 34, 33, 30, 26, 32, 28, 35, 29, 36, 31, 38, 37, 41, 40, 44, 39, 45, 43, 42, 48, 47, 51, 46, 49, 53, 55, 59, 60, 57, 50, 66, 75, 64, 54, 58, 62, 71, 52, 73, 79, 82, 84, 80, 56, 88, 61, 93, 68, 65, 67, 91
Offset: 1

Views

Author

Eric Angelini and Carole Dubois, May 24 2022

Keywords

Comments

This is the earliest permutation of the nonnegative integers with this property.

Examples

			The spiral begins:
.
     17--25--27--19--22--20
      |                   |
     21   5---8--11---7  24
      |   |           |   .
     23   6   0---1   9   .
      |   |       |   |   .
     18   3---4---2  10
      |               |
     16--13--15--14--12
.
The digits of the four integers inside each of the four 2 X 2 squares that contain the initial 0 add up to a prime: 0 + 1 + 2 + 4 = 7, 0 + 4 + 3 + 6 = 13, 0 + 6 + 5 + 8 = 19, 0 + 8 + (1+1) + 1 = 11. This is true for any 2 X 2 square on the (infinite) grid; the upper right corner adds up to 19, for instance: (2+2) + (2+0) + (2+4) + 7 = 19; etc.

Crossrefs

Cf. A337115, A337116, A337117, A337368, A354372.

A354374 Square spiral on a 2D square lattice, one term per cell, starting at the origin with 0; the digits of the four integers forming any 2 X 2 square add up to a prime and those sums themselves form another infinite 2D square lattice with the same property.

Original entry on oeis.org

0, 1, 2, 4, 3, 6, 5, 8, 11, 7, 9, 10, 12, 14, 17, 13, 15, 19, 39, 24, 16, 23, 29, 5999, 33, 18, 25, 42, 69, 699, 20, 26, 21, 999, 299, 599, 22, 28, 30, 31, 34, 38, 27, 37, 36, 40, 59, 4999, 43, 32, 35, 41, 49, 102, 47, 69999, 44, 45, 48, 99, 58, 52, 111, 689, 46, 51, 698, 79999, 9999999, 50, 68
Offset: 1

Views

Author

Eric Angelini and Carole Dubois, May 24 2022

Keywords

Comments

This is the earliest permutation of the nonnegative integers with this property.

Examples

			The spiral begins:
.
     16--23--29-5999-33--18
      |                   |
     24   5---8--11---7  25
      |   |           |   |
     39   6   0---1   9  42
      |   |       |   |   |
     19   3---4---2  10  69
      |               |   |
     15--13--17--14--12 699
                          |
        ... 999--21--26--20
.
The digits of the four integers inside each of the four 2 X 2 squares that contain the initial 0 add up to a prime: 0 + 1 + 2 + 4 = 7, 0 + 4 + 3 + 6 = 13, 0 + 6 + 5 + 8 = 19, 0 + 8 + (1+1) + 1 = 11. This is true for any 2 X 2 square on the (infinite) grid; the upper right corner adds up to the prime 29, for instance: (3+3) + (1+8) + (2+5) + 7 = 29; etc.
All those successive "prime sums" form the hereunder "second-level" spiral:
.
     37--19--43 ...
      |
     43  11--19--19--23
      |   |           |
     31  13   7--13  31
      |   |       |   |
     29  19--11--19  29
      |               |
     29--47--53--29--23
.
Though the terms of this new spiral are not distinct, the sum of the digits inside any 2 X 2 square is prime again; the upper left 2 X 2 square produces the prime 29 = (3+7) + (1+9) + (1+1) + (4+3); the lower left 2 X 2 square produces the prime 43 = (2+9) + (1+9) + (4+7) + (2+9); the lower right 2 X 2 square produces the prime 37 = (1+9) + (2+9) + (2+3) + (2+9); the initial "center square" produces the prime 23 = 7 + (1+3) + (1+9) + (1+1); etc.

Crossrefs

Cf. A337115, A337116, A337117, A337368, A354372, A354373, A354375.

A354375 Square spiral on a 2D square lattice, one term per cell, starting at the origin with 0; the digits of the four integers forming any 2 X 2 square add up to a square and those sums themselves form another infinite 2D square lattice with the same property.

Original entry on oeis.org

0, 1, 2, 6, 3, 999, 4, 5, 12, 7, 799, 8, 9, 89, 29, 79, 10, 88, 8999, 69, 11, 78, 39, 97, 19, 13, 87, 7999, 59, 14, 15, 169, 39999, 68, 49999, 699, 16, 22, 96, 159, 178, 21, 17, 599, 59999, 49, 58999, 168, 25, 18, 187, 100, 4999, 20, 177, 28, 23, 186, 89999, 99999, 199999, 98999, 9999, 77, 24, 27
Offset: 1

Views

Author

Eric Angelini and Carole Dubois, May 24 2022

Keywords

Comments

This is the earliest permutation of the nonnegative integers with this property.

Examples

			The spiral begins:
.
     11--78--39--97--19--13
      |                   |
     69   4---5--12---7  87
      |   |           |   |
   8999  999  0---1  799 7999
      |   |       |   |   |
     88   3---6---2   8  59
      |               |   |
     10--79--29--89---9  14
                          |
           ... 39999-169-15
.
The digits of the four integers inside each of the four 2 X 2 squares that contain the initial 0 add up to a square: 0 + 1 + 2 + 6 = 9, 0 + 6 + 3 + (9+9+9) = 36, 0 + 999 + 4 + 5 = 36, 0 + 5 + (1+2) + 1 = 9. This is true for any 2 X 2 square on the (infinite) grid; the digits of the upper right corner add up to 36, for instance: (1+9) + (1+3) + (8+7) + 7 = 36; the lower right 2 X 2 square produces 36 = 9 + (1+4) + (1+5) + (1+6+9); etc.
All those successive "square sums" form the hereunder "second-level" spiral:
.
       36---9--36--81
        |           |
       36   9--36  81
        |       |   |
       36--36--36  36
                    |
           ... 81--36
.
Though the terms of this new spiral are not distinct (only multiples of 9), the sum of the digits inside any 2 X 2 square is a square again; the upper left 2 X 2 square produces for instance the square 36 = (3+6) + 9 + 9 + (3+6); the lower left 2 X 2 square produces the square 36 again = (3+6) + 9 + (3+6) + (3+6); the lower right 2 X 2 square produces also the square 36 = (3+6) + (3+6) + (3+6) + (8+1); the initial "center square" produces the same 36 = 9 + (3+6) + (3+6) + (3+6); etc.

Crossrefs

Cf. A337115, A337116, A337117, A337368, A354372, A354373, A354374.
Showing 1-3 of 3 results.

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