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 A255200 #8 Feb 05 2017 03:36:35 %S A255200 17,28,41,281,2081,2801,4721,5441,6196,12161,12916,13996,20476,24916, %T A255200 32321,32441,34156,34961,40036,56596,70996,73361,94396 %N A255200 Numbers n such that triangular numbers T(n), T(n+1) and T(n+2) are 3-almost primes. %C A255200 Numbers n such that n, n+1 and n+2 are terms in A108815. %H A255200 Charles R Greathouse IV, <a href="/A255200/b255200.txt">Table of n, a(n) for n = 1..10000</a> %e A255200 T(17)=A000217(17)=153=3*3*17, T(18)=A000217(18)=171=3*3*19, T(19)=A000217(19)=171=2*5*19. %o A255200 (PARI) issemi(n)=bigomega(n)==2 %o A255200 is(n)=if(n%2, if(n%4==1, isprime((n+3)/4) && isprime(n+2) && isprime(n) && issemi((n+1)/2), isprime((n+1)/4) && isprime(n) && isprime(n+2) && issemi((n+3)/2)), if(n%4==2, isprime((n+2)/4) && isprime(n+1) && isprime(n+3) && issemi(n/2), isprime(n/4) && isprime(n+1) && isprime(n+3) && issemi(n/2+1))) \\ _Charles R Greathouse IV_, Feb 05 2017 %Y A255200 Cf. A000217, A075875, A108815. %K A255200 nonn %O A255200 1,1 %A A255200 _Zak Seidov_, Feb 16 2015