OFFSET
1,1
LINKS
Paolo Xausa, Table of n, a(n) for n = 1..10000
Dario Alpern, 4-Brilliant Numbers.
EXAMPLE
35321 is a term because 35321 = 11 * 13 * 13 * 19, and these four prime factors have the same number of digits.
MATHEMATICA
A376704Q[k_] := With[{f = FactorInteger[k]}, Total[f[[All, 2]]] == 4 && Length[Union[IntegerLength[f[[All, 1]]]]] == 1];
Select[Range[40000], A376704Q] (* or *)
dlist4[d_] := Sort[Times @@@ DeleteDuplicates[Map[Sort, Tuples[Prime[Range[PrimePi[10^(d-1)] + 1, PrimePi[10^d]]], 4]]]]; (* Generates terms with d-digits prime factors -- faster but memory intensive *)
Flatten[Array[dlist4, 2]]
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Paolo Xausa, Oct 02 2024
STATUS
approved