simple benchmarking

["Ruud H.G. van Tol" <rvtol@isolution.nl>]

? my(t0=getabstime()); for (n=1, 2^25-1, n-2^(#binary(n)-1)); 
printf("%.3fs",(getabstime()-t0)/1000)
14.434s

? my(t0=getabstime()); for (n=1, 2^25-1, n-2^logint(n,2)); 
printf("%.3fs",(getabstime()-t0)/1000)
10.600s

? my(t0=getabstime()); for (n=1, 2^25-1, n-2^exponent(n)); 
printf("%.3fs",(getabstime()-t0)/1000)
8.460s

See the PARI code in https://oeis.org/A053645

-- Ruud