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A363247
a(0) = 0. a(n) = the smallest nonnegative integer, excluding a(n-1), not occurring in all occurrences of a(n-1)'s eight neighbors thus far in a square spiral.
1
0, 1, 2, 3, 4, 1, 5, 2, 4, 5, 3, 6, 0, 7, 1, 8, 0, 9, 2, 8, 6, 4, 7, 8, 10, 0, 11, 1, 10, 2, 11, 4, 12, 2, 13, 3, 9, 5, 12, 3, 14, 0, 15, 1, 14, 5, 13, 4, 15, 2, 16, 1, 17, 0, 18, 1, 19, 0, 20, 1, 21, 0, 22, 1, 23, 0, 24, 1, 25, 0, 26, 1, 27, 0, 28, 2, 17, 3
OFFSET
0,3
LINKS
Scott R. Shannon, Image of the first 10000 terms on the square spiral. The value colors are scaled across the spectrum from red to violet to show their relative size. Zoom in to see the numbers.
EXAMPLE
The spiral begins:
0---8---1---7---0
| |
9 4---3---2 6
| | | |
2 1 0---1 3 .
| | | .
8 5---2---4---5 .
| |
6---4---7---8---10--0
a(0) = 0
a(1) = 1. Smallest integer that's not a neighbor to every 0 = 1.
a(2) = 2. Smallest integer that's not a neighbor to every 1 = 2.
a(3) = 3. Smallest integer that's not a neighbor to every 2 = 3.
a(4) = 4. Smallest integer that's not a neighbor to every 3 = 4.
a(5) = 1. Smallest integer that's not a neighbor to every 4 = 1.
CROSSREFS
Sequence in context: A278108 A302786 A322026 * A087165 A238326 A083480
KEYWORD
nonn
AUTHOR
Gavin Lupo, May 24 2023
STATUS
approved