A354947 Number of primes adjacent to prime(n) in a hexagonal spiral of positive integers.

2, 2, 0, 2, 1, 1, 0, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 1, 2, 0, 1, 0, 0, 0, 0, 0, 2, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 0

Offset: 1

Author

Wade Reece Eberly, Sep 23 2022

Keywords

• nonn
• easy

Examples

			The spiral begins
      13--12--11
      /         \
    14   4---3  10
    /   /     \   \
  15   5   1---2   9
    \   \         /
    16   6---7---8
      \
      17--18--19--...
For n=4, prime(4) = 7 in the spiral has a(4) = 2 primes adjacent (2 and 19).
		

Links

• Dimitri Tishchenko, Hexagon Prime Spiral

Crossrefs

Cf. A307011, A307013 (spiral coordinates), A056105 (spiral first spoke).