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A182857 Smallest number that requires exactly n iterations to reach a fixed point under the x -> A181819(x) map. 40

%I

%S 1,3,4,6,12,60,2520,1286485200,35933692027611398678865941374040400000

%N Smallest number that requires exactly n iterations to reach a fixed point under the x -> A181819(x) map.

%C a(9) has 296 digits.

%C Related to Levine's sequence (A011784): A011784(n) = A001222(a(n)) = A001221(a(n+1)) = A051903(a(n+2)) = A071625(a(n+2)). Also see A182858.

%C Values of n where A182850(n) increases to a record.

%C The multiplicity of prime(k) in a(n+1) is the k-th largest prime index of a(n), which is A296150(a(n),k). - _Gus Wiseman_, May 13 2018

%H Gus Wiseman, <a href="/A182857/b182857.txt">Table of n, a(n) for n = 0..9</a>

%F For n > 0, a(n) = A181819(a(n+1)). For n > 1, a(n) = A181821(a(n-1)).

%e From _Gus Wiseman_, May 13 2018: (Start)

%e Like A001462 the following sequence of multisets whose Heinz numbers belong to this sequence is a run-length describing sequence, as the number of k's in row n + 1 is equal to the k-th term of row n.

%e {2}

%e {1,1}

%e {1,2}

%e {1,1,2}

%e {1,1,2,3}

%e {1,1,1,2,2,3,4}

%e {1,1,1,1,2,2,2,3,3,4,4,5,6,7}

%e {1,1,1,1,1,1,1,2,2,2,2,2,2,3,3,3,3,3,4,4,4,4,5,5,5,5,6,6,6,7,7,7,8,8,9,9,10,10,11,12,13,14}

%e (End)

%t Prepend[Function[m,Times@@Prime/@m]/@NestList[Join@@Table[Table[i,{Reverse[#][[i]]}],{i,Length[#]}]&,{2},8],1] (* _Gus Wiseman_, May 13 2018 *)

%Y Cf. A001462, A007755, A007916, A009287, A012257, A112798, A181819, A182850-A182858, A296150, A304455, A304464, A304465.

%K nonn

%O 0,2

%A _Matthew Vandermast_, Jan 05 2011

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Last modified November 21 14:56 EST 2019. Contains 329371 sequences. (Running on oeis4.)