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A089827
Number of subsets of {1,.., n} containing no twin prime pairs.
2
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).
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
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Nov 12 2003
STATUS
approved