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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 (list; graph; refs; listen; history; text; internal format)
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 * A222089 A182763 A272709

Adjacent sequences:  A089824 A089825 A089826 * A089828 A089829 A089830

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Nov 12 2003

STATUS

approved

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Last modified September 17 19:16 EDT 2019. Contains 327137 sequences. (Running on oeis4.)