A107788 - OEIS

%I #13 Oct 07 2020 07:44:29

%S 1,8,11,64,88,121,512,704,968,1331,4096,5632,7744,10648,14641,32768,

%T 45056,61952,85184,117128,161051,262144,360448,495616,681472,937024,

%U 1288408,1771561,2097152,2883584,3964928,5451776,7496192,10307264

%N Numbers of the form (8^i)*(11^j), with i, j >= 0.

%H Reinhard Zumkeller, <a href="/A107788/b107788.txt">Table of n, a(n) for n = 1..10000</a>

%F Sum_{n>=1} 1/a(n) = (8*11)/((8-1)*(11-1)) = 44/35. - _Amiram Eldar_, Oct 07 2020

%F a(n) ~ exp(sqrt(2*log(8)*log(11)*n)) / sqrt(88). - _Vaclav Kotesovec_, Oct 07 2020

%t Take[Union[8^First[#]*11^Last[#]&/@Tuples[Range[0,20],2]],40] (* _Harvey P. Dale_, Jan 17 2015 *)

%t n = 10^6; Flatten[Table[8^i*11^j, {i, 0, Log[8, n]}, {j, 0, Log[11, n/8^i]}]] // Sort (* _Amiram Eldar_, Oct 07 2020 *)

%o (Haskell)

%o import Data.Set (singleton, deleteFindMin, insert)

%o a107788 n = a107788_list !! (n-1)

%o a107788_list = f $ singleton (1,0,0) where

%o    f s = y : f (insert (8 * y, i + 1, j) $ insert (11 * y, i, j + 1) s')

%o          where ((y, i, j), s') = deleteFindMin s

%o -- _Reinhard Zumkeller_, May 15 2015

%Y Cf. A025633, A025634, A107764, A003596, A003597, A107988, A003598, A003599, A108090.

%K nonn,easy

%O 1,2

%A Douglas Winston (douglas.winston(AT)srupc.com), Jun 14 2005