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.

Previous Showing 21-23 of 23 results.

A257333 Construct spiral of numbers on square grid as in Comments; sequence gives terms along the "2" arm.

Original entry on oeis.org

2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 35, 34, 33, 38, 37, 36, 41, 39, 43, 40, 47, 44, 45, 46, 49, 50, 53, 55, 42, 59, 51, 52, 57, 56, 61, 48, 65, 54, 67, 58, 63, 62, 71, 60, 73, 64
Offset: 1

Views

Author

N. J. A. Sloane, Apr 21 2015

Keywords

Comments

Place numbers 2,3,4,5 clockwise around a grid point (see illustration in "Spiral" link). Divide grid into four spiral arms.
Extend each arm one step at a time, in rotation: first the 2 arm, then the 3 arm, then the 4 arm, then the 5 arm, then the 2 arm, etc.
Rule for extending: next term in arm is smallest number such that each cell in the grid is relatively prime to its four (N,S,E,W) neighbors. Inside an arm, the terms must be distinct.
Repetitions between arms are permitted.
The "2" arm is the present sequence (A257333), the "3" arm is A257334. The "4" arm begins 4,3,2,5, and thereafter agrees with the "2" arm. The "5" arm begins 5,2,3,4, and thereafter agrees with the "3" arm.

Links

Crossrefs

Cf. A064413, A257321-A257340.

Extensions

More terms from Lars Blomberg, Apr 28 2015

A257334 Construct spiral of numbers on square grid as in Comments; sequence gives terms along the "3" arm.

Original entry on oeis.org

3, 2, 5, 4, 7, 8, 9, 11, 13, 6, 17, 10, 19, 14, 23, 12, 25, 16, 29, 15, 31, 22, 21, 20, 37, 18, 35, 24, 41, 26, 27, 28, 43, 32, 33, 34, 39, 38, 45, 44, 47, 30, 49, 36, 53, 40, 51, 46, 55, 42, 59, 48, 61, 50, 57, 52, 63, 58, 65, 54, 67, 56, 69, 71, 60, 73, 62
Offset: 1

Views

Author

N. J. A. Sloane, Apr 21 2015

Keywords

Comments

Place numbers 2,3,4,5 clockwise around a grid point (see illustration in "Spiral" link). Divide grid into four spiral arms.
Extend each arm one step at a time, in rotation: first the 2 arm, then the 3 arm, then the 4 arm, then the 5 arm, then the 2 arm, etc.
Rule for extending: next term in arm is smallest number such that each cell in the grid is relatively prime to its four (N,S,E,W) neighbors. Inside an arm, the terms must be distinct.
Repetitions between arms are permitted.
The "2" arm is A257333, the "3" arm is the present sequence (A257334). The "4" arm begins 4,3,2,5, and thereafter agrees with the "2" arm. The "5" arm begins 5,2,3,4, and thereafter agrees with the "3" arm.

Links

Crossrefs

Cf. A064413, A257321-A257340.

Extensions

Corrected a(25), a(29), a(30), a(32) and more terms from Lars Blomberg, Apr 28 2015

A257489 Arrange numbers in a single clockwise spiral so that each number is relatively prime to its 12 nearest neighbors.

Original entry on oeis.org

1, 2, 3, 5, 4, 7, 9, 11, 13, 15, 17, 19, 8, 23, 29, 27, 25, 31, 37, 10, 41, 43, 14, 47, 53, 16, 49, 59, 55, 21, 61, 65, 67, 22, 71, 73, 6, 77, 79, 39, 83, 89, 12, 91, 85, 57, 97, 101, 33, 35, 103, 107, 18, 109, 113, 32, 45, 121, 119, 81, 95, 127, 131, 115, 133
Offset: 1

Views

Author

Jon E. Schoenfield, Apr 26 2015

Keywords

Comments

In the illustration of initial terms (see Links), the 12 nearest neighbors of the first term are highlighted in yellow.

Links

Crossrefs

Cf. A064413, A257321-A257340.
Previous Showing 21-23 of 23 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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