Mountain nonprimes.

Terms

a(0) =1a(1) =121a(2) =141a(3) =161a(4) =171a(5) =1241a(6) =1251a(7) =1261a(8) =1271a(9) =1281a(10) =1341a(11) =1351a(12) =1371a(13) =1391a(14) =1421a(15) =1431a(16) =1461a(17) =1491a(18) =1521a(19) =1541a(20) =1561a(21) =1581a(22) =1591a(23) =1631a(24) =1641a(25) =1651a(26) =1671a(27) =1681a(28) =1691a(29) =1731