387840domain: NAppears in sequencessech(tan(x)*tan(x))=1-12/4!*x^4-480/6!*x^6-15792/8!*x^8...at n=5A012395Number of alignments of n points with no singleton cycles.at n=9A226226Numbers n such that phi(n) * tau(n) divides n^2, but neither tau(n) nor phi(n) divides n.at n=23A287800