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A096520 Number of primes in the neighborhood of center=2^n and radius=Ceiling[Log[2^n]]. 2
2, 3, 3, 3, 2, 3, 2, 2, 1, 3, 1, 3, 1, 1, 2, 3, 2, 5, 1, 4, 1, 2, 4, 2, 0, 2, 0, 2, 2, 5, 3, 3, 2, 0, 0, 3, 2, 2, 3, 2, 2, 3, 1, 4, 0, 2, 2, 1, 0, 2, 1, 2, 1, 1, 2, 2, 4, 1, 0, 1, 4, 0, 2, 2, 0, 3, 3, 2, 2, 2, 1, 1, 1, 3, 1, 3, 3, 3, 2, 1, 2, 4, 1, 3, 1, 3, 1, 1, 5, 3, 2, 1, 2, 2, 4, 2, 0, 4, 0, 1, 1, 2, 0, 2, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..105.

EXAMPLE

First in the suitable neighborhood of 2^25 no primes occur: a[25]=0, while around 2^127 6 primes arise: a[127]=6.

MATHEMATICA

t=Table[Count[Table[PrimeQ[2^n+i], {i, -Ceiling[Log[2^n]//N], Ceiling[Log[2^n]//N]}], True], {n, 1, 256}]

CROSSREFS

Cf. A096509-A096523.

Sequence in context: A293229 A185437 A210681 * A236552 A080748 A305374

Adjacent sequences:  A096517 A096518 A096519 * A096521 A096522 A096523

KEYWORD

nonn

AUTHOR

Labos Elemer, Jul 12 2004

STATUS

approved

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Last modified December 13 03:41 EST 2019. Contains 329968 sequences. (Running on oeis4.)