a(n) = 2*(10^(2n+1)-1)/9 - 10^n.A332121a(n) = 2*(10^(2n+1)-1)/9 - 10^n.Terms a(0) =1a(1) =212a(2) =22122a(3) =2221222a(4) =222212222a(5) =22222122222External referencesoeis: A332121