A160686 - OEIS

%I #17 Aug 09 2017 22:03:01

%S 1,2,4,8,16,32,64

%N Numbers n such that n/A000005(A000045(n)) is an integer.

%C The first power of 2 not in this sequence is 2^7 = 128, because 128/A000005(A000045(128)) = 1/2, which is not an integer. - _Nathaniel Johnston_, May 08 2011

%C Next term, if it exists, is greater than 3000. Conjecture: the sequence is finite and complete. - _Max Alekseyev_, May 21 2011

%F {n: A063375(n) | n}. - _R. J. Mathar_, May 25 2009

%p with(combinat):with(numtheory): A160686 := proc(n) option remember: local k: if(n=1)then return 1:fi: for k from procname(n-1)+1 do if(k mod tau(fibonacci(k))=0)then return k:fi: od: end: seq(A160686(n),n=1..7); # _Nathaniel Johnston_, May 08 2011

%Y Cf. A000005, A000045, A000079, A160683.

%K nonn,hard,more

%O 1,2

%A _Ctibor O. Zizka_, May 23 2009

%E Inverted division in the definition - _R. J. Mathar_, May 25 2009

%E Erroneous term a(5) = 12 removed by _Nathaniel Johnston_, May 08 2011