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

Author

Reinhard Zumkeller, Nov 12 2003

Keywords

• nonn

Comments

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

Crossrefs

Cf. A071538, A001359, A006512.

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.