112925716858domain: NAppears in sequencesIndices of triangular numbers which are also heptagonal.at n=9A039835a(n) = F(3) + F(6) + F(9) + ... + F(3n), F(n) = Fibonacci numbers A000045.at n=18A099919Lower (1/2)-midsequence of (F(2n)) and (F(2n+1)), where F=A000045 (Fibonacci numbers); see Comments.at n=27A387778