|
|
A176877
|
|
Numbers that are the product of 3 distinct primes a,b and c, such that a+b+c are prime numbers.
|
|
5
|
|
|
165, 273, 345, 385, 399, 435, 561, 595, 651, 665, 715, 759, 777, 795, 885, 903, 957, 1001, 1015, 1065, 1085, 1173, 1209, 1235, 1281, 1335, 1435, 1443, 1463, 1495, 1515, 1533, 1547, 1551, 1615, 1645, 1659, 1677, 1705, 1749, 1767, 1771, 1885, 1947, 1965
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
165=3*5*11; 3+5+11=19,...
|
|
LINKS
|
|
|
MATHEMATICA
|
l[n_]:=Last/@FactorInteger[n]; f[n_]:=First/@FactorInteger[n]; lst={}; Do[If[l[n]=={1, 1, 1}, a=f[n][[1]]; b=f[n][[2]]; c=f[n][[3]]; If[PrimeQ[a+b+c], AppendTo[lst, n]]], {n, 7!}]; lst
With[{upto=2000}, Select[Times@@@Select[Subsets[Prime[Range[ PrimePi[ upto/6]]], {3}], PrimeQ[Total[#]]&]//Union, #<=upto&]] (* Harvey P. Dale, May 15 2017 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|