65645domain: NAppears in sequencesa(1)=1. a(2n+1) = sum{k=1 to 2n} a(k). a(2n) = the smallest positive integer not yet occurring in the sequence.at n=28A140598a(n) = Sum_{k=1..n} k^2*phi(k), where phi is the Euler totient function A000010.at n=24A319087