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A151969 a(n) = smallest integer >= n which has only prime factors 2 and 5. 4
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

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 *)

PROG

(R) f <- function(n) nextn(n, factors = c(2, 5))

a <- matrix(1:256, ncol=1)

apply(a, 1, f)

CROSSREFS

Cf. A130916, A134361, A151970.

Sequence in context: A327625 A084824 A184615 * A261393 A327629 A121528

Adjacent sequences:  A151966 A151967 A151968 * A151970 A151971 A151972

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Aug 23 2009

STATUS

approved

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Last modified July 14 16:21 EDT 2020. Contains 335729 sequences. (Running on oeis4.)