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A136627
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For every number n in Ulam's spiral the sequence gives the number of primes around it (number n included).
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1
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4, 3, 4, 3, 3, 3, 3, 3, 3, 2, 4, 5, 4, 2, 2, 2, 3, 3, 4, 3, 3, 2, 3, 2, 1, 0, 2, 3, 4, 3, 3, 2, 3, 1, 2, 2, 3, 3, 3, 2, 3, 3, 3, 1, 1, 2, 3, 2, 1, 1, 1, 1, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 1, 3, 3, 3, 1, 2, 3, 5, 4, 4, 3, 2, 0, 1, 2, 2, 1, 1, 1, 1, 1, 2, 2, 2, 1, 2, 2, 1, 0, 2, 2, 4, 3, 3, 1, 0, 1, 1, 2
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| In Ulam's lattice there are 8 numbers around any number. The sequence is similar to A136626 with an increment of 1 for any prime position.
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EXAMPLE
| n=13: numbers around 13 are 3, 12, 29, 30, 31, 32, 33, 14 -> 3, 29, 31 and 13 itself are primes -> 4.
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CROSSREFS
| Cf. A063826, A115258, A136626.
Sequence in context: A058290 A002285 A106049 * A108171 A106055 A171783
Adjacent sequences: A136624 A136625 A136626 * A136628 A136629 A136630
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KEYWORD
| easy,nonn
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AUTHOR
| Paolo P. Lava & Giorgio Balzarotti (paoloplava(AT)gmail.com), Jan 14 2008
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