Number of distinct Cunningham chains of first kind whose initial prime (cf. A059453) <= 2^n.

Terms

a(0) =1a(1) =2a(2) =2a(3) =2a(4) =3a(5) =5a(6) =7a(7) =13a(8) =20a(9) =31a(10) =52a(11) =83a(12) =142a(13) =242a(14) =412a(15) =742a(16) =1308a(17) =2294a(18) =4040a(19) =7327a(20) =13253a(21) =24255a(22) =44306a(23) =81700a(24) =150401a(25) =277335a(26) =513705a(27) =954847a(28) =1780466a(29) =3325109