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 A213741 #10 Feb 05 2017 19:06:38
%S A213741 5,13,20,23,24,35,39,41,42,43,47,50,56,61,62,63,67,68,69,70,73,76,78,
%T A213741 81,86,90,98,112,123,126,128,134,143,145,147,160,165,166,172,176,180,
%U A213741 182,186,189,191,193,196,197,200,215,220,222,223,225,227,229,238
%N A213741 Numbers n such that the sum of the first n primes is divisible by exactly 3 prime powers (not including 1).
%C A213741 This is to "triprimes" or "3-almost primes" A014612 as A213650 is to semiprimes A001358.
%H A213741 Charles R Greathouse IV, <a href="/A213741/b213741.txt">Table of n, a(n) for n = 1..10000</a>
%F A213741 {n such that A007504(n) is included in A014612.}
%e A213741 a(1) = 5 because the sum of first 5 primes is 28 = 2^2 * 7 which has exactly three prime power factors (not including 1).
%e A213741 a(2) = 13 because the sum of first 13 primes is 238 = 2 * 7 * 17 which has exactly three prime power factors (not including 1).
%e A213741 a(3) = 20 because the sum of first 20 primes is 639 = 3^2 * 71.
%t A213741 ps = 0; t = {}; Do[ps = ps + Prime[n]; If[Total[Transpose[FactorInteger[ps]][[2]]] == 3, AppendTo[t, n]], {n, 300}]; t (* _T. D. Noe_, Jun 27 2012 *)
%o A213741 (PARI) list(lim)=my(v=List(),k,s); forprime(p=2,prime(lim\1), k++; if(bigomega(s+=p)==3, listput(v,k))); Vec(v) \\ _Charles R Greathouse IV_, Feb 05 2017
%Y A213741 Cf. A007504, A014612, A213650.
%K A213741 nonn,easy
%O A213741 1,1
%A A213741 _Jonathan Vos Post_, Jun 19 2012