a(n) = 4*(10^(2*n+1)-1)/9 + 3*10^n.A332147a(n) = 4*(10^(2*n+1)-1)/9 + 3*10^n.Terms a(0) =7a(1) =474a(2) =44744a(3) =4447444a(4) =444474444a(5) =44444744444External referencesoeis: A332147