OFFSET
1,2
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
FORMULA
Sum_{n>=1} 1/a(n) = (2*9)/((2-1)*(9-1)) = 9/4. - Amiram Eldar, Sep 24 2020
a(n) ~ exp(sqrt(2*log(2)*log(9)*n)) / sqrt(18). - Vaclav Kotesovec, Sep 24 2020
MAPLE
N:= 10^5: # for terms <= N
sort([seq(seq(2^i*9^j, i=0..ilog2(N/9^j)), j=0..floor(log[9](N)))]); # Robert Israel, Mar 23 2020
MATHEMATICA
Take[Union[2^First[#] 9^Last[#]&/@Tuples[Range[0, 20], {2}]], 50] (* Harvey P. Dale, May 26 2011 *)
n = 10^5; Flatten[Table[2^i*9^j, {i, 0, Log[2, n]}, {j, 0, Log[9, n/2^i]}]] // Sort (* Amiram Eldar, Sep 24 2020 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
STATUS
approved