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.

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

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)

A151969 a(n) = smallest integer >= n which has only prime factors 2 and 5.

Original entry on oeis.org

1, 2, 4, 4, 5, 8, 8, 8, 10, 10, 16, 16, 16, 16, 16, 16, 20, 20, 20, 20, 25, 25, 25, 25, 25, 32, 32, 32, 32, 32, 32, 32, 40, 40, 40, 40, 40, 40, 40, 40, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 80, 80, 80, 80, 80
Offset: 1

Views

Author

N. J. A. Sloane, Aug 23 2009

Keywords

Links

Crossrefs

Cf. A130916, A134361, A151970.

Programs

  • Mathematica
    Module[{upto=100,pwr,f25},pwr=Ceiling[Log[2,upto]];f25=Select[ Sort[ Flatten[ Table[Times@@@Union[Sort/@Tuples[{2,5},n]],{n,0,pwr}]]],#<= upto&]; Table[SelectFirst[f25,#>i&],{i,0,upto-1}]] (* The program uses the SelectFirst function from Mathematica version 10 *) (* Harvey P. Dale, Jan 28 2016 *)
  • R
    f <- function(n) nextn(n, factors = c(2,5))
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

Cf. A130916, A134361, A151969.

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.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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