Partial sums of A005200.

Terms

a(0) =1a(1) =3a(2) =7a(3) =18a(4) =46a(5) =124a(6) =337a(7) =935a(8) =2605a(9) =7328a(10) =20684a(11) =58670a(12) =166863a(13) =476032a(14) =1360955a(15) =3899324a(16) =11191494a(17) =32173714a(18) =92625281a(19) =267010344a(20) =770610783a(21) =2226438062a(22) =6438902174a(23) =18638275524a(24) =53995855636a(25) =156548609636a(26) =454200201824