631714domain: NAppears in sequencesNumbers k such that 10*R_k + 7 is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=21A056655Number of colored integer partitions of 2n such that all colors from an n-set are used.at n=8A340987Expansion of (-1 + Product_{k>=1} 1 / (1 - x^k))^8.at n=8A341227