A098908 Sorted products of primes (2,3,5,7...) and factorials (1,2,6,24...).

2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 17, 18, 19, 22, 23, 26, 29, 30, 31, 34, 37, 38, 41, 42, 43, 46, 47, 48, 53, 58, 59, 61, 62, 66, 67, 71, 72, 73, 74, 78, 79, 82, 83, 86, 89, 94, 97, 101, 102, 103, 106, 107, 109, 113, 114, 118, 120, 122, 127, 131, 134, 137, 138, 139

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

In the set of products of primes and factorials 10 (= 5 times factorial 2) is the seventh largest number and therefore is the seventh member of the sequence.

Maple

N:= 1000: # to get all terms <= N
P:= select(isprime, [2, seq(i, i=3..N, 2)]):
F:= 1: v:= 1:
for n from 2 do
  v:= v*n;
  if v > N then break fi;
  F:= F, v;
od:
F:= {F}:
sort(convert(select(`<=`, {seq(seq(p*f, f=F), p=P)}, N), list)); # Robert Israel, Aug 27 2018

Mathematica

With[{upto=140}, Select[Union[Flatten[Table[p*f, {p, Prime[ Range[ PrimePi[ upto]]]}, {f, Range[10]!}]]], #<=upto&]] (* Harvey P. Dale, Jul 19 2019 *)

Crossrefs

Cf. A000040, A000142.

Sequence in context: A074946 A279455 A050687 * A097296 A131616 A175857

Adjacent sequences: A098905 A098906 A098907 * A098909 A098910 A098911

Keyword

nonn

Author

Axel Harvey, Oct 15 2004

Status

approved