Number of solutions to sigma(x) = n!.

Terms

a(0) =1a(1) =0a(2) =1a(3) =3a(4) =4a(5) =15a(6) =33a(7) =111a(8) =382a(9) =1195a(10) =3366a(11) =14077a(12) =53265a(13) =229603a(14) =910254a(15) =4524029a(16) =18879944a(17) =91336498a(18) =561832582a(19) =2801857644a(20) =14652294729a(21) =78894985156a(22) =408373652461