458561domain: NAppears in sequencesNumber of centered hydrocarbons with n atoms.at n=21A000022Incorrect version of A091967.at n=21A031135Incorrect version of A107357.at n=21A037181a(n) is the n-th term of sequence A_n, ignoring the offset, or -1 if A_n has fewer than n terms.at n=21A091967