The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A095816 Number of permutations of 1..n with no three elements in correct or reverse order. 10
 1, 1, 2, 4, 18, 92, 570, 4082, 33292, 304490, 3086890, 34357812, 416526730, 5463479106, 77094352076, 1164544912938, 18749754351338, 320544941916628, 5799226664694602, 110695180631374114, 2223242026407894732 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Counts permutations with the property that no subsequence i(i+1)(i+2) or (i+2)(i+1)i occurs. LINKS Andrew Howroyd, Table of n, a(n) for n = 0..200 W. M. Dymacek, I. Lambert, Permutations Avoiding Runs of i, i+1, i+2 or i, i-1, i-2 , J. Int. Seq. 14 (2011) # 11.1.6, Table 1. D. M. Jackson and R. C. Read, A note on permutations without runs of given length, Aequationes Math. 17 (1978), no. 2-3, 336-343. FORMULA G.f. Sum_{n>=0} n!*((2*x^m-x^(m+1)-x)/(x^m-1))^n where m = 3. - Ivana Jovovic ( ivana121(AT)EUnet.yu ), Nov 11 2007 PROG (PARI) seq(n)={my(m=3); Vec(sum(k=0, n, k!*((2*x^m-x^(m+1)-x)/(x^m-1) + O(x*x^n))^k))} \\ Andrew Howroyd, Aug 31 2018 CROSSREFS Cf. A002464, A095817, A095818. Cf. A165963, A165964, A078628. [From Isaac Lambert, Oct 07 2009] Sequence in context: A295370 A292280 A120664 * A020101 A099938 A135069 Adjacent sequences:  A095813 A095814 A095815 * A095817 A095818 A095819 KEYWORD nonn AUTHOR Jonas Wallgren, Jun 08 2004 EXTENSIONS More terms from Ivana Jovovic ( ivana121(AT)EUnet.yu ), Nov 11 2007 a(0)=1 prepended by Max Alekseyev, Jun 14 2011 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.

Last modified July 5 05:10 EDT 2022. Contains 355087 sequences. (Running on oeis4.)