|
|
A113839
|
|
Powerful numbers (definition 1) sandwiched between twin primes.
|
|
8
|
|
|
4, 72, 108, 432, 1152, 2592, 3528, 9000, 18252, 20808, 21600, 34848, 49392, 69192, 83232, 103968, 139968, 180000, 197568, 264600, 345600, 362952, 438048, 444528, 472392, 649800, 734472, 808992, 995328, 1143072, 1190700, 1254528, 1529388, 1685448, 1960200, 2056752
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
Here we are considering powerful numbers defined in A001694.
|
|
LINKS
|
|
|
EXAMPLE
|
72 = 2^3*3^2 is powerful and 71 and 73 are twin primes, so 72 is in the sequence.
|
|
MATHEMATICA
|
pwfQ[n_] := n == 1 || Min[Transpose[FactorInteger@n][[2]]] > 1; lst={}; Do[If[PrimeQ[n-1] && PrimeQ[n+1] && pwfQ[n], AppendTo[lst, n]], {n, 4, 2*10^6, 4}]; lst
|
|
PROG
|
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|