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A136627

For every number n in Ulam's spiral the sequence gives the number of primes around it (number n included).

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, 3, 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

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OFFSET

1,1

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.

LINKS

Table of n, a(n) for n=1..102.

EXAMPLE

Numbers around 13 are 3, 12, 29, 30, 31, 32, 33, 14 -> 3, 29, 31 and 13 itself are primes, so a(13)=4.

CROSSREFS

Cf. A063826, A115258, A136626.

Sequence in context: A238234 A367439 A367126 * A108171 A231475 A106055