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A010761
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a(n) = floor(n/2) + floor(n/3).
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10
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0, 1, 2, 3, 3, 5, 5, 6, 7, 8, 8, 10, 10, 11, 12, 13, 13, 15, 15, 16, 17, 18, 18, 20, 20, 21, 22, 23, 23, 25, 25, 26, 27, 28, 28, 30, 30, 31, 32, 33, 33, 35, 35, 36, 37, 38, 38, 40, 40, 41, 42, 43, 43, 45, 45, 46, 47, 48, 48, 50, 50, 51, 52, 53, 53, 55, 55, 56, 57, 58, 58, 60, 60
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OFFSET
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1,3
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LINKS
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FORMULA
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G.f.: x^2*(1+2*x+2*x^2)/((1-x^2)*(1-x^3)).
a(-n) = -2-a(n-1). (End)
Sum_{n>=2} (-1)^n/a(n) = sqrt(2*(1-1/sqrt(5)))*Pi/10 + log(phi)/sqrt(5), where phi is the golden ratio (A001622). - Amiram Eldar, Mar 30 2023
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MAPLE
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seq(floor(n/2) + floor(n/3), n=1..64);
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MATHEMATICA
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LinearRecurrence[{0, 1, 1, 0, -1}, {0, 1, 2, 3, 3}, 80] (* Harvey P. Dale, May 05 2018 *)
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PROG
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(PARI) a(n)=n\2+n\3
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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