The number of nonnegative integers that have a shortest divisor addition chain of length n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =5a(5) =9a(6) =14a(7) =25a(8) =41a(9) =76a(10) =128a(11) =229a(12) =389a(13) =710a(14) =1238a(15) =2258a(16) =3986a(17) =7211a(18) =13000a(19) =23609a(20) =42839a(21) =78271a(22) =142924a(23) =262541a(24) =481347a(25) =887753a(26) =1637365a(27) =3027681a(28) =5604228a(29) =10397802