OFFSET
1,2
COMMENTS
The density of this sequence is 1 - 2*log_10(2) = 0.3979400086720376...
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
FORMULA
floor(log_10(2)*k) = floor(log_10(2)*(k+1)) = floor(log_10(2)*(k+2)).
EXAMPLE
2^4 = 16, 2^5 = 32, 2^6 = 64: all these numbers have two digits.
2^10 = 1024, 2^11 = 2048, 2^12 = 4096: all these numbers have three digits.
MAPLE
select(n -> ilog10(2^n)=ilog10(2^(n+2)), [$1..1000]); # Robert Israel, May 19 2019
MATHEMATICA
Select[Range[220], Floor[Log[10, 2]*# ] == Floor[Log[10, 2]*(# + 2)] &]
PROG
(Magma) [k:k in [1..160]|#Intseq(2^k) eq #Intseq(2^(k+2))]; // Marius A. Burtea, May 20 2019
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Stefan Steinerberger, Mar 11 2006
STATUS
approved