OFFSET
1,1
COMMENTS
These are the numbers of the form p^3*q (with primes p and q distinct) or p^7. Thus it is the union of A065036 and A092759, and this can be used for direct enumeration. - Alex Meiburg, Dec 31 2017
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
Caldwell and Honaker, Prime Curios!
Wikipedia, Sphenic number
FORMULA
MAPLE
N:= 1000: # to get all terms <= N
P:= select(isprime, [2, seq(i, i=3..N)]):
R:= NULL:
for p in P do
if p^7 <= N then R:= R, p^7 fi;
if p^3 > N then break fi;
for q in P while p^3*q <= N do if q <> p then R:= R, p^3*q fi od:
od:
sort([R]); # Robert Israel, Dec 31 2017
MATHEMATICA
Select[Range@ 1200, And[DivisorSigma[0, #] == 8, Nand[PrimeNu[#] == 3, PrimeOmega[#] == 3]] &] (* Michael De Vlieger, Dec 29 2017 *)
PROG
(PARI) isok(n) = !((bigomega(n)==3) && (omega(n)==3)) && (numdiv(n) == 8); \\ Michel Marcus, Dec 29 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
G. L. Honaker, Jr., Dec 29 2017
EXTENSIONS
More terms from Michel Marcus, Dec 29 2017
STATUS
approved