OFFSET
1,2
COMMENTS
Numbers that are not members of A000215.
FORMULA
For n > 2, a(n) = n+m+2 if n+m>=4^(2^m) and a(n) = n+m+1 otherwise where m = floor(log_2(log_2(n-1))). - Chai Wah Wu, Oct 19 2024
MATHEMATICA
Complement[Range[10000], {3, 5, 17, 257}] (* Harvey P. Dale, Aug 04 2023 *)
PROG
(Python)
def A138888(n): return n+(m:=((n-1).bit_length()-1).bit_length() if n>2 else 0)+(n+m>=(1<<(1<<m))+1) # Chai Wah Wu, Oct 19 2024
CROSSREFS
KEYWORD
easy,nonn,changed
AUTHOR
Omar E. Pol, Apr 03 2008
STATUS
approved