This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A006840 Number of 2n-bead black-white reversible complementable necklaces with n black beads. (Formerly M0837) 6
 1, 1, 2, 3, 7, 13, 35, 85, 257, 765, 2518, 8359, 28968, 101340, 361270, 1297879, 4707969, 17179435, 63068876, 232615771, 861725794, 3204236779, 11955836258, 44748176653, 167959144032, 632058070310, 2384235077576, 9013628451275 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 REFERENCES J. A. Hoskins, C. E. Praeger and A. P. Street, Balanced twills with bounded float length, Congress. Numerantium, 40 (1983), 77-89. W. D. Hoskins; Anne Penfold Street, Twills on a given number of harnesses, J. Austral. Math. Soc. Ser. A 33 (1982), no. 1, 1-15. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS FORMULA If n is odd, 1/2 (A045629 + 1/2 C(n-1, (n-1)/2) + 2^(n-2)); if n is even, 1/2 (A045629 + 1/2 C(n, n/2) + 2^(n-2)) (Christian Bower). CROSSREFS Sequence in context: A129859 A056953 A045611 * A123408 A033995 A013917 Adjacent sequences:  A006837 A006838 A006839 * A006841 A006842 A006843 KEYWORD nonn AUTHOR EXTENSIONS More terms from David W. Wilson. STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
Recent Additions | More pages | Superseeker | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .