A115741 Semiprimes (A001358) whose digit reversal is a triangular number.
6, 10, 51, 55, 82, 87, 309, 501, 649, 694, 1198, 1207, 1473, 1765, 1803, 1837, 1959, 1981, 3043, 3057, 3561, 3574, 5158, 5221, 5721, 6139, 6193, 6267, 6535, 6711, 6814, 6843, 10473, 10497, 11553, 12477, 12693, 13123, 13701, 13951, 14169
Offset: 1
Examples
51=3*17 is semiprime and 15=T(5).