login
A078541
Refactorable numbers x, such that quotient x/A000005(x) equals a power of 2.
1
1, 2, 8, 12, 36, 80, 96, 128, 288, 448, 2560, 6144, 11264, 18432, 32768, 53248, 57344, 245760, 737280, 1114112, 2621440, 4980736, 22020096, 23068672, 25165824, 66060288, 75497472, 96468992, 436207616, 939524096, 1258291200, 1811939328, 2147483648, 3774873600
OFFSET
1,2
LINKS
FORMULA
a(n)/tau(a(n))=2^s with some s, tau()=A000005()
EXAMPLE
a(6)=80: tau(80)=10, quotient=80/10=8=2^3; certain powers of 2 do not appear as quotient, like 64, 1024, 16384.
MATHEMATICA
Do[s=n/DivisorSigma[0, n]; If[IntegerQ[Log[2, s]], Print[{n, s, n/s}]], {n, 1, 1000000000}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Dec 04 2002
EXTENSIONS
a(29)-a(34) from Donovan Johnson, Jun 04 2011
STATUS
approved