Number of idempotent n X n 0..3 matrices of rank n-1.

Terms

a(0) =1a(1) =14a(2) =93a(3) =508a(4) =2555a(5) =12282a(6) =57337a(7) =262136a(8) =1179639a(9) =5242870a(10) =23068661a(11) =100663284a(12) =436207603a(13) =1879048178a(14) =8053063665a(15) =34359738352a(16) =146028888047a(17) =618475290606