cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-3 of 3 results.

A130916 a(n) = smallest integer >= n which has only prime factors 2, 3 and 5.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 8, 8, 9, 10, 12, 12, 15, 15, 15, 16, 18, 18, 20, 20, 24, 24, 24, 24, 25, 27, 27, 30, 30, 30, 32, 32, 36, 36, 36, 36, 40, 40, 40, 40, 45, 45, 45, 45, 45, 48, 48, 48, 50, 50, 54, 54, 54, 54, 60, 60, 60, 60, 60, 60, 64, 64, 64, 64, 72, 72, 72, 72, 72
Offset: 1

Views

Author

N. J. A. Sloane, Aug 23 2009

Keywords

Comments

This group of sequences is useful when looking for a number >= n to use as the basis for a Fast Fourier Transform when you have n data points.

Crossrefs

Programs

  • Mathematica
    si[n_]:=Module[{k=n},While[Max[FactorInteger[k][[All,1]]]>5,k++];k]; Array[ si,70] (* Harvey P. Dale, Oct 14 2019 *)
  • R
    f <- function(n) nextn(n, factors = c(2,3,5))
    a <- matrix(1:256,ncol=1)
    apply(a,1,f)

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

Original entry on oeis.org

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

Views

Author

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

Keywords

Comments

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

Crossrefs

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)
    

A151970 a(n) = smallest integer >= n which has only prime factors 3 and 5.

Original entry on oeis.org

1, 3, 3, 5, 5, 9, 9, 9, 9, 15, 15, 15, 15, 15, 15, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 27, 27, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75
Offset: 1

Views

Author

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

Keywords

Crossrefs

Programs

  • R
    f <- function(n) nextn(n, factors = c(3,5))
    a <- matrix(1:256,ncol=1)
    apply(a,1,f)
Showing 1-3 of 3 results.