Pentagonal numbers (A000326) whose digit reversal is a semiprime (A001358).

Terms

a(0) =12a(1) =22a(2) =51a(3) =176a(4) =330a(5) =532a(6) =590a(7) =715a(8) =782a(9) =925a(10) =1162a(11) =1247a(12) =1335a(13) =1426a(14) =1717a(15) =3151a(16) =3290a(17) =4187a(18) =5551a(19) =7107a(20) =7315a(21) =7957a(22) =10542a(23) =10795a(24) =11051a(25) =11837a(26) =12376a(27) =14950a(28) =15251a(29) =15555