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 A128054 List the nonnegative integers where multiples of 6 occur twice and numbers of the form 6k+4 are omitted. 3
 0, 0, 1, 2, 3, 5, 6, 6, 7, 8, 9, 11, 12, 12, 13, 14, 15, 17, 18, 18, 19, 20, 21, 23, 24, 24, 25, 26, 27, 29, 30, 30, 31, 32, 33, 35, 36, 36, 37, 38, 39, 41, 42, 42, 43, 44, 45, 47, 48, 48, 49, 50, 51, 53, 54, 54, 55, 56, 57, 59, 60, 60, 61, 62, 63, 65, 66, 66 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS Table of n, a(n) for n=0..67. Index entries for linear recurrences with constant coefficients, signature (2,-2,2,-2,2,-1). FORMULA a(n) = a(n-6) + 6, for n >= 6. a(n) = cos(2*Pi*n/3)/6-sqrt(3)*sin(2*Pi*n/3)/6+cos(Pi*n/3)/2-sqrt(3)*sin(Pi*n/3)/6+(3n-2)/3. G.f.: x^2*(x^3+x^2+1) / ((x-1)^2*(x^2-x+1)*(x^2+x+1)). - Colin Barker, Jun 27 2013 Sum_{n>=2} (-1)^n/a(n) = 5*Pi/(12*sqrt(3)) - log(3)/4 + log(2)/3. - Amiram Eldar, Apr 04 2023 MATHEMATICA fix[n_]:=Which[Divisible[n, 6], {n, n}, Mod[n, 6]==4, {}, True, n]; Flatten[ fix/@ Range[0, 70]] (* Harvey P. Dale, Aug 21 2014 *) CROSSREFS Sequence in context: A165083 A165085 A309560 * A175081 A023834 A084735 Adjacent sequences: A128051 A128052 A128053 * A128055 A128056 A128057 KEYWORD easy,nonn AUTHOR Paul Barry, Feb 13 2007 STATUS approved

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Last modified August 14 04:13 EDT 2024. Contains 375146 sequences. (Running on oeis4.)