A096521 Smallest exponent of 2 when the number of primes in the neighborhood of center=2^n and radius=ceiling(log(2^n)) equals n.

25, 9, 1, 2, 20, 18, 127, 844, 573

Offset

0,1

Links

Table of n, a(n) for n=0..8.

Example

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

Mathematica

t=Table[Count[Table[PrimeQ[2^n+i], {i, -Ceiling[Log[2^n]//N], Ceiling[Log[2^n]//N]}], True], {n, 1, 256}] Table[Min[Flatten[Position[t, j]]], {j, 0, 10}]

Crossrefs

Cf. A096509-A096523.

Sequence in context: A040605 A307179 A065910 * A215539 A224490 A226224

Adjacent sequences: A096518 A096519 A096520 * A096522 A096523 A096524

Keyword

nonn,more

Author

Labos Elemer, Jul 12 2004

Status

approved