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 A066751 #10 Dec 15 2017 17:35:48
%S A066751 3,91,136,325,703,1081,1378,1711,3655,11026,11476,13861,18145,18721,
%T A066751 36046,70876,75466,76636,79003,92665,99235,107416,108811,110215,
%U A066751 118828,123256,130816,137026,140185,158203,166753,173755,186355,303031,310078
%N A066751 Triangular numbers whose reverse is prime.
%H A066751 Harry J. Smith, <a href="/A066751/b066751.txt">Table of n, a(n) for n = 1..1000</a>
%o A066751 (PARI) Rev(x)= { local(d, r=0); while (x>0, d=x%10; x\=10; r=r*10 + d); return(r) } { n=0; for (m=1, 10^10, t=m*(m + 1)/2; if (t%10 && isprime(Rev(t)), write("b066751.txt", n++, " ", t); if (n==1000, return)) ) } \\ _Harry J. Smith_, Mar 21 2010
%K A066751 easy,nonn,base
%O A066751 1,1
%A A066751 _Jason Earls_, Jan 16 2002