103689domain: NAppears in sequencesa(n) = n + floor(Sum_{k<n} a(k)/2) with a(0)=0.at n=27A079719A089450 indexed by A000040.at n=34A089525Numbers n such that n-1, n and n+1 can be expressed as a sum of 2 squares in at least 2 ways.at n=18A091459