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 A140222 #12 Feb 19 2019 23:34:38
%S A140222 2,3,9,11,13,14,28,29,31,34,35,51,54,56,61,81,83,93,94,97,98,123,124,
%T A140222 131,140,142,171,173,177,179,180,185,187,190,191,193,195,228,230,231,
%U A140222 233,234,248,251,290,293,294,296,297,304,309,310,315,316,320,322,373
%N A140222 A number j is included if (Sum_{k=1..j} d(k)) is prime, where d(k) is the number of divisors of k.
%C A140222 Sum_{k=1..j} d(k) = Sum_{k=1..j} floor(j/k) = A006218(j).
%H A140222 Michael De Vlieger, <a href="/A140222/b140222.txt">Table of n, a(n) for n = 1..10000</a>
%e A140222 9 is in the sequence because the number of divisors of 1,2,...,9 are 1,2,2,3,2,4,2,4,3, respectively, having as sum the prime number 23.
%p A140222 with(numtheory): a:=proc(n) if isprime(sum(tau(k),k=1..n))=true then n else end if end proc: seq(a(n),n=1..400); # _Emeric Deutsch_, Jun 08 2008
%t A140222 Position[Accumulate@ DivisorSigma[0, Range@ 400], _?PrimeQ][[All, 1]] (* _Michael De Vlieger_, Feb 19 2019 *)
%Y A140222 Cf. A006218, A140221.
%K A140222 nonn
%O A140222 1,1
%A A140222 _Leroy Quet_, May 12 2008
%E A140222 More terms from _Emeric Deutsch_, Jun 08 2008