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A056415
Number of step cyclic shifted sequences using exactly two different symbols.
2
0, 1, 2, 4, 4, 11, 8, 22, 20, 43, 28, 156, 72, 243, 366, 691, 520, 2635, 1608, 7384, 8866, 19399, 16768, 94482, 67560, 216273, 277532, 815556, 662368, 4500265, 2311468, 8466187, 13045106, 31593283, 40937604, 159772174, 103197488, 401913695
OFFSET
1,3
COMMENTS
See A056371 for an explanation of step shifts. Under step cyclic shifts, abcde, bdace, bcdea, cdeab and daceb etc. are equivalent.
REFERENCES
M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]
FORMULA
a(n) = A002729(n) - 2.
CROSSREFS
Cf. A002729.
Sequence in context: A202076 A199825 A121049 * A242993 A366045 A263382
KEYWORD
nonn
EXTENSIONS
Added more terms (from A002729), Joerg Arndt, Aug 27 2014
STATUS
approved