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A136626 For every number n in Ulam's spiral the sequence gives the number of primes around it (number n excluded). 16
4, 2, 3, 3, 2, 3, 2, 3, 3, 2, 3, 5, 3, 2, 2, 2, 2, 3, 3, 3, 3, 2, 2, 2, 1, 0, 2, 3, 3, 3, 2, 3, 3, 1, 2, 2, 2, 3, 3, 2, 2, 3, 2, 1, 1, 2, 2, 2, 1, 1, 1, 1, 1, 2, 3, 2, 2, 2, 1, 2, 1, 2, 2, 1, 3, 3, 2, 1, 2, 3, 4, 4, 3, 3, 2, 0, 1, 2, 1, 1, 1, 1, 0, 1, 2, 2, 2, 1, 1, 2, 1, 0, 2, 2, 4, 3, 2, 1, 0, 1, 0, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
In Ulam's lattice there are 8 numbers around any number.
LINKS
EXAMPLE
Numbers around 13 are 3, 12, 29, 30, 31, 32, 33, 14 -> 3, 29, 31 are primes, so a(13)=3.
CROSSREFS
Sequence in context: A345996 A190874 A307367 * A079623 A177864 A090112
KEYWORD
easy,nonn
AUTHOR
EXTENSIONS
Offset 1 per example and correction for a(32) by Kevin Ryde, Jul 04 2020
STATUS
approved

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Last modified March 28 04:13 EDT 2024. Contains 371235 sequences. (Running on oeis4.)