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 A123046 Number of frieze patterns of length n under a certain group (see Pisanski et al. for precise definition). 1
 0, 1, 4, 6, 23, 52, 194, 586, 2131, 7286, 26524, 95326, 350738, 1290556, 4798174, 17895736, 67127315, 252645136, 954510114, 3616814566, 13744183772, 52357696956, 199912348954, 764877654106, 2932035552786, 11258999068468, 43303860638644, 166799986203766 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Table of n, a(n) for n=0..27. T. Pisanski, D. Schattschneider and B. Servatius, Applying Burnside's lemma to a one-dimensional Escher problem, Math. Mag., 79 (2006), 167-180. See G(n). FORMULA See Maple program. MAPLE V:=proc(n) local k, t1; t1:=0; for k in divisors(n) do t1 := t1+phi(k)*4^(n/k); od: t1; end; H:=n-> if n mod 2 = 0 then (n/2)*4^(n/2); else 0; fi; R:=proc(n) local k, t1; t1:=0; for k in divisors(n) do if k mod 2 = 0 then t1 := t1+phi(k)*4^(n/k); fi; od: t1; end; A123046:=n->(V(n)+2*H(n)+R(n))/(4*n); CROSSREFS Sequence in context: A075813 A107952 A004032 * A237748 A359863 A326233 Adjacent sequences: A123043 A123044 A123045 * A123047 A123048 A123049 KEYWORD nonn AUTHOR N. J. A. Sloane, Nov 11 2006 STATUS approved

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Last modified July 21 02:16 EDT 2024. Contains 374462 sequences. (Running on oeis4.)