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A254783
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Numbers n such that A033493(n)/n is an integer.
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0
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1, 57, 847, 1694, 3039, 3388, 3479, 6078, 6776, 6958, 13916, 27832, 55664, 111328, 236107, 246721, 311257, 493442, 622514, 986884, 1245028, 1328233, 1973768, 2052521, 2490056, 2656466, 3947536, 4105042, 4980112, 8210084
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OFFSET
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1,2
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COMMENTS
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If A033493(n)/n = M is even, then 2*n is a member of the sequence and A033493(2*n)/(2*n) = M/2 + 1.
Sum of reciprocals seems to converge quickly to 1.0208... - Derek Orr, Mar 12 2015
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LINKS
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MATHEMATICA
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a033493[n_] := Block[{f}, f[1] = 1; f[x_Integer?OddQ] := 3 x + 1; f[x_Integer?EvenQ] := x/2; -1 + Plus @@ FixedPointList[f, n]]; Select[Range[10^5], IntegerQ[a033493[#]/#] &] (* Michael De Vlieger, Feb 09 2015, after Alonso del Arte at A033493 *)
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PROG
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(PARI) Tsum(n)=s=n; while(n!=1, if(n==Mod(0, 2), n=n/2; s+=n); if(n==Mod(1, 2)&&n!=1, n=3*n+1; s+=n)); s
for(n=1, 10^6, if(type(Tsum(n)/n)=="t_INT", print1(n, ", ")))
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CROSSREFS
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KEYWORD
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nonn,more,hard
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AUTHOR
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STATUS
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approved
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