Smallest prime of the form Sum_{i=0..k} binomial(n,i), or a(n)=0 if there is no such a prime.

Terms

a(0) =2a(1) =3a(2) =7a(3) =5a(4) =31a(5) =7a(6) =29a(7) =37a(8) =0a(9) =11a(10) =67a(11) =13a(12) =1093a(13) =1471a(14) =9949a(15) =17a(16) =131071a(17) =19a(18) =191a(19) =211a(20) =7547a(21) =23a(22) =277a(23) =190051a(24) =1807781a(25) =61450327a(26) =379a(27) =29a(28) =0a(29) =31