A336576 The final square number for a walk on a square spiral numbered board when starting on square 1 and stepping to an unvisited square containing the lowest prime number, where the square is within a block of size (2n+1) x (2n+1) centered on the current square. If no unvisited prime numbered squares exist within the block the walk ends.

59, 947, 313, 3331, 5659, 67547, 253801, 676259, 3162413, 16604417, 29135971, 108235159, 437456497

Offset

1,1

Comments

See A336494 for an explanation of the sequence and images of the walks.

Links

Table of n, a(n) for n=1..13.

Wikipedia, Ulam Spiral.

Example

a(1) = 59. Starting from the square 1 the sequence of adjacent unvisited lowest primes the walk can step to are 2,3,11,29,13,31,59. Once the square 59 is visited there are no other unvisited adjacent squares containing primes, so the walk terminates.

Crossrefs

Cf. A336494 (total number of steps), A335856, A000040, A136626, A336092, A330979, A332767, A335661, A335364.

Sequence in context: A142363 A215433 A093259 * A248974 A245941 A248620

Adjacent sequences: A336573 A336574 A336575 * A336577 A336578 A336579

Keyword

nonn,walk,more

Author

Scott R. Shannon, Jul 26 2020

Status

approved