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A136626
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For every number n in Ulam's spiral the sequence gives the number of primes around it (number n excluded).
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16
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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
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OFFSET
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1,1
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COMMENTS
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In Ulam's lattice there are 8 numbers around any number.
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LINKS
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EXAMPLE
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Numbers around 13 are 3, 12, 29, 30, 31, 32, 33, 14 -> 3, 29, 31 are primes, so a(13)=3.
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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Offset 1 per example and correction for a(32) by Kevin Ryde, Jul 04 2020
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STATUS
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approved
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