305472domain: NAppears in sequencesTheta series of direct sum of 4 copies of hexagonal lattice.at n=21A008655G.f.: Sum_{n>=0} x^(n*(n+1)/2) / Product_{k=1..n} (1 - k*x^k).at n=32A204856Number of (n+2) X 7 0..2 matrices with each 3 X 3 subblock idempotent.at n=20A224603