A089827 Number of subsets of {1,.., n} containing no twin prime pairs.

2, 4, 8, 16, 24, 48, 80, 160, 320, 640, 1280, 2560, 3840, 7680, 15360, 30720, 61440, 122880, 184320, 368640, 737280, 1474560, 2949120, 5898240, 11796480, 23592960, 47185920, 94371840, 188743680, 377487360, 566231040

Offset

1,1

Comments

a(n) = A000079(n) - A089828(n).

Links

Table of n, a(n) for n=1..31.

Formula

a(n) = if n and n-2 are primes then (if n=7 then a(n-1)*5/3 else a(n-1)*3/2) else a(n-2)*2.

Crossrefs

Cf. A071538, A001359, A006512.

Sequence in context: A225549 A138278 A326078 * A369151 A222089 A182763

Adjacent sequences: A089824 A089825 A089826 * A089828 A089829 A089830

Keyword

nonn

Author

Reinhard Zumkeller, Nov 12 2003

Status

approved