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A354947
Number of primes adjacent to prime(n) in a hexagonal spiral of positive integers.
0
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
1,1
EXAMPLE
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).
CROSSREFS
Cf. A307011, A307013 (spiral coordinates), A056105 (spiral first spoke).
Sequence in context: A322523 A333210 A285193 * A213209 A049850 A319954
KEYWORD
nonn,easy
AUTHOR
Wade Reece Eberly, Sep 23 2022
STATUS
approved