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A047248
Numbers that are congruent to {0, 2, 3, 4, 5} (mod 6).
2
0, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 20, 21, 22, 23, 24, 26, 27, 28, 29, 30, 32, 33, 34, 35, 36, 38, 39, 40, 41, 42, 44, 45, 46, 47, 48, 50, 51, 52, 53, 54, 56, 57, 58, 59, 60, 62, 63, 64, 65, 66, 68
OFFSET
1,2
FORMULA
G.f.: x^2*(2+x+x^2+x^3+x^4) / ( (x^4+x^3+x^2+x+1)*(x-1)^2 ). - R. J. Mathar, Oct 08 2011
Sum_{n>=2} (-1)^n/a(n) = log(2+sqrt(3))/(2*sqrt(3)) + log(2)/6 - (9-4*sqrt(3))*Pi/36. - Amiram Eldar, Dec 17 2021
MATHEMATICA
Rest[CoefficientList[Series[x^2*(2 + x + x^2 + x^3 + x^4)/((x^4 + x^3 + x^2 + x + 1)*(x - 1)^2), {x, 0, 50}], x]] (* G. C. Greubel, Nov 02 2017 *)
DeleteCases[Range[0, 70], _?(Mod[#, 6]==1&)] (* or *) Complement[ Range[ 0, 70], Range[1, 70, 6]] (* Harvey P. Dale, Dec 30 2017 *)
PROG
(PARI) x='x+O('x^50); concat([0], Vec(x^2*(2+x+x^2+x^3+x^4)/((x^4 +x^3 +x^2 +x+1)*(x-1)^2))) \\ G. C. Greubel, Nov 02 2017
CROSSREFS
Cf. A047252.
Sequence in context: A032798 A195122 A184520 * A114024 A030173 A048265
KEYWORD
nonn
STATUS
approved