dsyr2k(3) on Linux
The text 6037b59d67d1, as Debian 8 (Jessie), Debian 7 (Wheezy), Debian 6.0 (Squeeze), Debian 5.0 (Lenny), Debian 4.0 (Etch), Debian 3.1 (Sarge) shipped it.
perform one of the symmetric rank 2k operations C := alpha*A*B' + alpha*B*A' + beta*C,