Number of idempotent 7 X 7 0..n matrices of rank 6.

Terms

a(0) =889a(1) =10199a(2) =57337a(3) =218743a(4) =653177a(5) =1647079a(6) =3670009a(7) =7440167a(8) =13999993a(9) =24801847a(10) =41803769a(11) =67575319a(12) =105413497a(13) =159468743a(14) =234881017a(15) =337925959a(16) =476171129a(17) =658642327a(18) =895999993a(19) =1200725687a(20) =1587318649a(21) =2072502439a(22) =2675441657