%I M2589 #26 Mar 02 2022 20:59:39
%S 1,0,1,3,6,15,42,109,320,979,3137,10603,37728,140423,546859,2220294,
%T 9374309,41059926,186149869,871717073,4208841555,20917405824,
%U 106849492793
%N Occurrences of principal character.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H Russell Merris and William Watkins, <a href="https://doi.org/10.1137/0604054">Tensors and graphs</a>, SIAM J. Algebraic Discrete Methods 4 (1983), no. 4, 534-547.
%Y Cf. A259976.
%Y Possibly row n = 2 of A331509.
%K nonn,more
%O 0,4
%A _N. J. A. Sloane_
%E a(7)-a(17) from _Andrey Zabolotskiy_, Sep 10 2018
%E a(18)-a(22) from _Sean A. Irvine_, Mar 02 2022