a(n) is the number of primes that can be written as +-1! +- 2! +- 3! +- ... +- n!.

Terms

a(0) =0a(1) =1a(2) =3a(3) =4a(4) =7a(5) =11a(6) =16a(7) =29a(8) =42a(9) =72a(10) =121a(11) =191a(12) =367a(13) =693a(14) =1215a(15) =2221a(16) =4116a(17) =7577a(18) =13900a(19) =25634a(20) =48322a(21) =90046a(22) =169016a(23) =317819a(24) =600982a(25) =1138049a(26) =2158939a(27) =4103414a(28) =7818761a(29) =14923641