cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

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

Original entry on oeis.org

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

Views

Author

Reinhard Zumkeller, Nov 12 2003

Keywords

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.

A089882 Number of subsets of {1, ..., n} containing exactly one twin prime pair.

Original entry on oeis.org

0, 0, 0, 0, 8, 16, 32, 64, 128, 256, 512, 1024, 768, 1536, 3072, 6144, 12288, 24576, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432, 20971520, 41943040, 83886080, 167772160
Offset: 1

Views

Author

Reinhard Zumkeller, Nov 13 2003

Keywords

Crossrefs

Cf. A071538, A089827, A089828, A001359, A006512.

Formula

a(n) = ceiling(A089881(n)/2)*2^(n-A089881(n)).
Showing 1-2 of 2 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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