The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A089264 Number of permutations of length n containing exactly once 132 and 213, likewise for pattern pair (231,312). 1
3, 6, 17, 42, 102, 242, 564, 1296, 2944, 6624, 14784, 32768, 72192, 158208, 345088, 749568, 1622016, 3497984, 7520256, 16121856, 34471936, 73531392, 156499968, 332398592, 704643072, 1491075072, 3149922304, 6643777536, 13992198144 (list; graph; refs; listen; history; text; internal format)
OFFSET
4,1
LINKS
Aaron Robertson, Permutations restricted by two distinct patterns of length three, arXiv:math/0012029 [math.CO], 2000.
FORMULA
For n>=7, a(n) = (n^2+21*n-28)*2^(n-9).
G.f.: x^4*(x-1)^2*(2*x^3-2*x^2+6*x-3) / (2*x-1)^3. [Colin Barker, Jan 31 2013]
MATHEMATICA
LinearRecurrence[{6, -12, 8}, {3, 6, 17, 42, 102, 242}, 40] (* Harvey P. Dale, Apr 10 2022 *)
CROSSREFS
Cf. A001815.
Sequence in context: A297972 A275057 A320807 * A121399 A212421 A238428
KEYWORD
nonn,easy
AUTHOR
Ralf Stephan, Oct 30 2003
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 27 12:27 EDT 2024. Contains 372858 sequences. (Running on oeis4.)