1,1

a(d) is number of parts d-dimensional space (x_1,...,x_d) is split into by set of (2^d - 1) hyper-planes c_1 x_1 + c_2 x_2 + ...+ c_d x_d =0 where c_j are 0 or +1 and we exclude case with all c=0. It is also number of independent real-time Green functions of Qunatum Field Theory produced when analytically continuing from euclidean time/energy (d+1 = number of energy/time variables.)

M. van Eijck, Thermal Field Theory and Finite-Temperature Renormalisation Group, PhD thesis, Univ. Amsterdam, 4th Dec. 1995.

T. S. Evans, N-point finite temperature expectation values at real times, Nuclear Physics B 374 (1992) 340-370.

T. S. Evans, What is being calculated with thermal field theory?, preprint hep-ph/9404262.

Most recent paper (see table 1).

a(2)=6 because we can split two dimensional space into 6 parts using lines x=0, y=0 and x+y=0.

Adjacent sequences: A034994 A034995 A034996 this_sequence A034998 A034999 A035000

Sequence in context: A055612 A056642 A001199 this_sequence A067735 A118077 A013976

nonn,more

Tim S. Evans (T.Evans(AT)ic.ac.uk)