Semiprimes (A001358) whose digit reversal is a pentagonal number (A000326).

Terms

a(0) =10a(1) =15a(2) =21a(3) =22a(4) =235a(5) =287a(6) =517a(7) =529a(8) =671a(9) =1513a(10) =1555a(11) =2611a(12) =5137a(13) =5331a(14) =6241a(15) =7017a(16) =7171a(17) =7421a(18) =7597a(19) =7814a(20) =10078a(21) =10913a(22) =15011a(23) =15094a(24) =15214a(25) =15251a(26) =20395a(27) =20603a(28) =21542a(29) =23129