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A080671
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Numbers having divisors 2 or 3 or 5.
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5
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2, 3, 4, 5, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 74, 75, 76, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 92, 93, 94, 95, 96, 98
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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The asymptotic density of this sequence is 11/15. - Amiram Eldar, Dec 07 2020
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (2,-2,2,-2,2,-2,2,-2,2,-2,2,-2,2,-2,2,-2,2,-2,2,-2,2,-1).
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FORMULA
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G.f.: x *( 2 -x +2*x^2 -x^3 +2*x^4 +x^6 +2*x^8 +x^10 +2*x^12 +x^14 +2*x^16 -x^17 +2*x^18 -x^19 +2*x^20 ) / ( (x^10 -x^9 +x^8 -x^7 +x^6 -x^5 +x^4 -x^3 +x^2 -x+1)*(1 +x +x^5 +x^6 +x^7 +x^8 +x^9 +x^2 +x^4 +x^3 +x^10)*(x-1)^2 ). - R. J. Mathar, Jul 11 2024
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MAPLE
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A080671 := proc(n) local s; option remember;
s:=[2, 3, 4, 5, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30];
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MATHEMATICA
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Select[Range[98], Mod[#, 2]*Mod[#, 3]*Mod[#, 5] == 0 &] (* T. D. Noe, Oct 07 2013 *)
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PROG
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(PARI) div235(n) = { for(x=1, n, if(gcd(x, 30)<>1, print1(x", ")) ) }
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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