Number of ways of arranging row n of the prime pyramid.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =2a(7) =4a(8) =7a(9) =24a(10) =80a(11) =216a(12) =648a(13) =1304a(14) =3392a(15) =13808a(16) =59448a(17) =155464a(18) =480728a(19) =1588162a(20) =5626309a(21) =28279112a(22) =157469880a(23) =842498189a(24) =4998554801a(25) =28466978744a(26) =166572523589