A134361 a(n) = smallest integer >= n which has only prime factors 2 and 3.

1, 2, 3, 4, 6, 6, 8, 8, 9, 12, 12, 12, 16, 16, 16, 16, 18, 18, 24, 24, 24, 24, 24, 24, 27, 27, 27, 32, 32, 32, 32, 32, 36, 36, 36, 36, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 54, 54, 54, 54, 54, 54, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 72, 72, 72, 72, 72, 72, 72, 72

Offset: 1

Author

N. J. A. Sloane, Aug 23 2009; corrected Mar 07 2012

Keywords

• nonn
• easy

Comments

Can be used, for example, to derive A084788 and A084790 from A084789. - Charles R Greathouse IV, Jul 09 2021

Crossrefs

Cf. A130916, A134361, A151969.

Programs

Mathematica

With[{pf23=Union[Flatten[Table[Times@@@Tuples[{2,3},n],{n,0,6}]]]}, Flatten[Table[Select[pf23,#>=n&,1],{n,80}]]] (* Harvey P. Dale, Mar 07 2012 *)

PARI

a(n)=my(v=List()); for(i=0,logint(n,3)+1, my(t=3^i); t<<=if(t>n, 0, exponent(n\t)+1); listput(v,t)); Set(v)[1] \\ Charles R Greathouse IV, Jul 09 2021

R

f <- function(n) nextn(n, factors = c(2,3))
a <- matrix(1:256,ncol=1)
apply(a,1,f)