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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). 2
 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, 2, 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 0,1 COMMENTS In Ulam's lattice there are 8 numbers around any number. LINKS EXAMPLE n=13: numbers around 13 are 3, 12, 29, 30, 31, 32, 33, 14 -> 3, 29, 31 are primes -> 3 CROSSREFS Cf. A063826, A115258, A136627. Sequence in context: A106644 A190874 A307367 * A079623 A177864 A090112 Adjacent sequences:  A136623 A136624 A136625 * A136627 A136628 A136629 KEYWORD easy,nonn AUTHOR Paolo P. Lava and Giorgio Balzarotti, Jan 14 2008 STATUS approved

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Last modified December 14 07:03 EST 2019. Contains 329978 sequences. (Running on oeis4.)