931861domain: NAppears in sequencesa(1) = 1, a(2n) = smallest composite number > (2n-1)-th partial sum of the sequence itself and a(2n+1) = smallest prime > 2n-th partial sum of the sequence.at n=19A076975Numbers k such that concatenation of k and its 10's complement is a palindromic prime.at n=9A109627