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A120942 3-smooth numbers 2^i*3^j where i and j are regular 3-smooth numbers. 0
6, 12, 18, 24, 36, 48, 54, 72, 108, 144, 162, 192, 216, 324, 432, 576, 648, 768, 1296, 1458, 1536, 1728, 2304, 2916, 4608, 5184, 5832, 6912, 11664, 12288, 13122, 13824, 20736, 26244, 36864, 39366, 41472, 46656, 52488, 78732, 104976, 110592, 157464 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..43.

EXAMPLE

54 is in the list because it is 2^1*3^3 and 1 and 3 are 3-smooth numbers.

MAPLE

interface(prettyprint=0) ; isA003586 := proc(n) local ifa, f, bas ; ifa := op(2, ifactors(n)) ; for f from 1 to nops(ifa) do bas := op(1, op(f, ifa)) ; if bas > 3 then RETURN(false) ; fi ; od ; RETURN(true) ; end: isA120942 := proc(n) local ifa, f, bas, expo ; ifa := op(2, ifactors(n)) ; if nops(ifa) <> 2 then RETURN(false) ; fi ; for f from 1 to nops(ifa) do bas := op(1, op(f, ifa)) ; if bas > 3 then RETURN(false) ; else expo := op(2, op(f, ifa)) ; if not isA003586(expo) then RETURN(false) ; fi ; fi ; od ; RETURN(true) ; end: for n from 2 to 40000 do if isA120942(n) then printf("%d, ", n) ; fi ; od; # R. J. Mathar, Aug 23 2006

CROSSREFS

Cf. A003586.

Sequence in context: A215142 A033845 A187778 * A147306 A031478 A073455

Adjacent sequences:  A120939 A120940 A120941 * A120943 A120944 A120945

KEYWORD

nonn

AUTHOR

Ben Paul Thurston, Aug 18 2006

EXTENSIONS

Corrected and extended by Ray Chandler and R. J. Mathar, Aug 23 2006

STATUS

approved

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Last modified October 19 04:40 EDT 2019. Contains 328211 sequences. (Running on oeis4.)