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A261141 Positive integers n that can be expressed as a product of Jacobsthal numbers (A001045), not necessarily distinct. 1
1, 3, 5, 9, 11, 15, 21, 25, 27, 33, 43, 45, 55, 63, 75, 81, 85, 99, 105, 121, 125, 129, 135, 165, 171, 189, 215, 225, 231, 243, 255, 275, 297, 315, 341, 363, 375, 387, 405, 425, 441, 473, 495, 513, 525, 567, 605, 625, 645, 675, 683, 693, 729, 765, 825, 855, 891, 903, 935, 945 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

EXAMPLE

15 is in the sequence because Jacobsthal numbers 3 and 5 multiply to 15.

MAPLE

N:= 10000: # to get all terms <= N

J:= gfun:-rectoproc({a(n)=a(n-1)+2*a(n-2), a(0)=0, a(1)=1}, a(n), remember):

P:= {1};

for j from 3 to ilog2(N*3+1) do

  x:= J(j);

  P:= `union`(seq(select(`<=`, map(`*`, P, x^k), N), k=0..floor(log[x](N))))

od:

sort(convert(P, list)); # Robert Israel, Nov 19 2015

MATHEMATICA

max = 11; jacobProds = Table[(2^n - (-1)^n)/3, {n, 2, max]; curr = 2; While[jacobProds[[curr]] < 2^max/3, jacobProds = Union[jacobProds, jacobProds[[curr]] * jacobProds]; curr++]; Select[jacobProds, # < 2^max/3 &] (* Alonso del Arte, Nov 18 2015 *)

CROSSREFS

Cf. A001045.

Sequence in context: A104635 A210537 A199407 * A283594 A233764 A233780

Adjacent sequences:  A261138 A261139 A261140 * A261142 A261143 A261144

KEYWORD

nonn

AUTHOR

Jeffrey Shallit, Nov 18 2015

STATUS

approved

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Last modified April 18 16:52 EDT 2019. Contains 322216 sequences. (Running on oeis4.)