cp's OEIS Frontend

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

%I A182857 #27 May 19 2018 19:20:45
%S A182857 1,3,4,6,12,60,2520,1286485200,35933692027611398678865941374040400000
%N A182857 Smallest number that requires exactly n iterations to reach a fixed point under the x -> A181819(x) map.
%C A182857 a(9) has 296 digits.
%C A182857 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 A182857 Values of n where A182850(n) increases to a record.
%C A182857 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 A182857 Gus Wiseman, <a href="/A182857/b182857.txt">Table of n, a(n) for n = 0..9</a>
%F A182857 For n > 0, a(n) = A181819(a(n+1)). For n > 1, a(n) = A181821(a(n-1)).
%e A182857 From _Gus Wiseman_, May 13 2018: (Start)
%e A182857 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 A182857 {2}
%e A182857 {1,1}
%e A182857 {1,2}
%e A182857 {1,1,2}
%e A182857 {1,1,2,3}
%e A182857 {1,1,1,2,2,3,4}
%e A182857 {1,1,1,1,2,2,2,3,3,4,4,5,6,7}
%e A182857 {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 A182857 (End)
%t A182857 Prepend[Function[m,Times@@Prime/@m]/@NestList[Join@@Table[Table[i,{Reverse[#][[i]]}],{i,Length[#]}]&,{2},8],1] (* _Gus Wiseman_, May 13 2018 *)
%Y A182857 Cf. A001462, A007755, A007916, A009287, A012257, A112798, A181819, A182850-A182858, A296150, A304455, A304464, A304465.
%K A182857 nonn
%O A182857 0,2
%A A182857 _Matthew Vandermast_, Jan 05 2011