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 A208994 Number of 3-bead necklaces labeled with numbers -n..n not allowing reversal, with sum zero and first differences in -n..n. 1
 1, 1, 3, 5, 7, 11, 15, 19, 25, 31, 37, 45, 53, 61, 71, 81, 91, 103, 115, 127, 141, 155, 169, 185, 201, 217, 235, 253, 271, 291, 311, 331, 353, 375, 397, 421, 445, 469, 495, 521, 547, 575, 603, 631, 661, 691, 721, 753, 785, 817, 851, 885, 919, 955, 991, 1027, 1065, 1103, 1141 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..10000 (first 210 terms from R. H. Hardin) Index entries for linear recurrences with constant coefficients, signature (2,-1,1,-2,1) FORMULA a(n) = 2*a(n-1) - a(n-2) + a(n-3) - 2*a(n-4) + a(n-5). From Alois P. Heinz, Mar 07 2018: (Start) a(n) = 1 + floor(n*(n+1)/3). G.f.: -(x^2+1)*(x^2-x+1)/((x^2+x+1)*(x-1)^3). (End) EXAMPLE All 15 solutions for n=6: -2 -1 -3 -2 -2 -1 -1 -3 -2 -3 -4 0 -2 -3 -2 1 -1 3 0 3 1 0 2 -1 0 2 0 -2 1 2 1 2 0 2 -1 0 1 1 3 3 2 0 4 2 0 CROSSREFS Row n=3 of A208993. Sequence in context: A219655 A335039 A007665 * A194602 A337217 A333380 Adjacent sequences: A208991 A208992 A208993 * A208995 A208996 A208997 KEYWORD nonn AUTHOR R. H. Hardin, Mar 04 2012 EXTENSIONS a(0)=1 prepended by Alois P. Heinz, Mar 07 2018 STATUS approved

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Last modified September 22 18:10 EDT 2023. Contains 365531 sequences. (Running on oeis4.)