A239586 Prime factor >= other prime factor of n-th brilliant number, cf. A078972.

2, 3, 3, 5, 7, 5, 7, 5, 7, 7, 11, 13, 13, 17, 19, 17, 19, 23, 17, 23, 29, 19, 31, 19, 29, 23, 31, 37, 23, 41, 43, 37, 29, 47, 31, 23, 41, 29, 43, 53, 31, 47, 37, 59, 29, 61, 53, 41, 37, 31, 43, 67, 59, 41, 71, 61, 47, 73, 43, 29, 37, 79, 67, 47, 31, 53, 83

Offset: 1

Author

Reinhard Zumkeller, Mar 22 2014

Keywords

• nonn
• look
• base

Comments

a(n) = A006530(A078972(n)) = A078972(n) / A239585(n).

A055642(a(n)) = A055642(A239585(n)).

Examples

			See A239585.
		

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..20000
• Dario Alpern, Brilliant Numbers

Crossrefs

Subsequence of A084127.

Cf. A006530, A055642, A078972, A239585.

Programs

Haskell

a239586 n = a078972 n `div` a239585 n

Mathematica

Table[With[{f = FactorInteger[k]}, If[Total[f[[All, 2]]] == 2 && Length[Union[IntegerLength[f[[All, 1]]]]] == 1, f[[-1, 1]], Nothing]], {k, 1000}] (* Paolo Xausa, Oct 02 2024 *)
dlist2[d_] := Union[Times @@@ Tuples[Prime[Range[PrimePi[10^(d-1)] + 1, PrimePi[10^d]]], 2]]; (* Generates terms with d-digits prime factors -- faster but memory intensive *)
Map[FactorInteger[#][[-1,1]]&,Flatten[Array[dlist2,2]]] (* Paolo Xausa, Oct 08 2024 *)