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 A103301 Number of perfect rulers with n segments (n>=0). 4
 1, 1, 3, 9, 24, 88, 254, 1064, 1644, 3382, 4156, 8022, 26264, 52012, 25434, 8506, 5632, 6224, 12330 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS For definitions, references and links related to complete rulers see A103294. LINKS FORMULA a(n) = Sum(A103300(i), i from A004137(n)+1 to A004137(n+1)), (n>=1) EXAMPLE a(3)=9 counts the perfect rulers with 3 segments, {[0,1,2,4],[0,2,3,4], [0,1,3,4],[0,1,3,5],[0,2,4,5],[0,1,2,5],[0,3,4,5],[0,1,4,6],[0,2,5,6]}. CROSSREFS Cf. A103300, A103297, A103296 (Complete rulers with n segments), A103299 (Optimal rulers with n segments). Sequence in context: A090577 A047114 A290511 * A148920 A204448 A032681 Adjacent sequences:  A103298 A103299 A103300 * A103302 A103303 A103304 KEYWORD nonn,hard AUTHOR Peter Luschny Feb 28 2005 STATUS approved

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