This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A115742 #4 Nov 14 2013 09:04:46 %S A115742 6,15,28,55,78,105,120,190,496,780,903,946,1176,1225,1275,1540,1653, %T A115742 1770,1830,1891,2080,3081,3403,3486,3570,3741,3916,4186,4753,5050, %U A115742 5356,5671,6670,7021,7140,7381,7503,7626,8515,8911,9316,9591,9870 %N A115742 Triangular numbers whose digit reversal is a semiprime (A001358). %H A115742 Harvey P. Dale, <a href="/A115742/b115742.txt">Table of n, a(n) for n = 1..1000</a> %e A115742 15=T(5) and 51=3*17 is semiprime. %t A115742 Select[Accumulate[Range[200]],PrimeOmega[FromDigits[Reverse[ IntegerDigits[ #]]]] == 2&] (* _Harvey P. Dale_, Nov 14 2013 *) %Y A115742 Cf. A001358, A115741. %K A115742 nonn,base %O A115742 1,1 %A A115742 _Giovanni Resta_, Jan 31 2006