Duplicate of A076048.

Terms

a(0) =1a(1) =4a(2) =11a(3) =26a(4) =52a(5) =109a(6) =237a(7) =556a(8) =1405a(9) =3690a(10) =10085a(11) =28157a(12) =80071a(13) =230568a(14) =670122