a(n) = c is least number such that 10^n/2 -/+ c are primes.

Terms

a(0) =0a(1) =3a(2) =9a(3) =81a(4) =123a(5) =57a(6) =87a(7) =243a(8) =69a(9) =63a(10) =189a(11) =231a(12) =1569a(13) =381a(14) =231a(15) =1443a(16) =1113a(17) =321a(18) =339a(19) =1353a(20) =363a(21) =519a(22) =1323a(23) =1503a(24) =741a(25) =1221a(26) =957a(27) =1053a(28) =339a(29) =5931