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 A065870 #22 Apr 30 2015 12:17:36
%S A065870 -2,-3,-4,-3,-3,-2,-4,-3,-2,3,-2,3,6,5,8,7,10,10,12,14,15,17,18,20,23,
%T A065870 24,21,22,23,26,36,38,43,44,43,40,42,45,48,52,57,58,62,60,63,58,69,80,
%U A065870 82,83,78,81,82,90,91,94,92,93,94,96,96,99,106,109,110,112,125,128,134,135,138,142,149,154,158,157,154,160,154,160
%N A065870 n-th prime - n-th semiprime.
%H A065870 Harry J. Smith, <a href="/A065870/b065870.txt">Table of n, a(n) for n = 1..1000</a>
%F A065870 a(n) = A000040(n) - A001358(n). - _Zak Seidov_, Apr 29 2015
%e A065870 Prime_1 - semiprime_1 = 2 - 4 = -2, prime_2 - semiprime_2 = 3 - 6 = -3, prime_3 - semiprime_3 = 5 - 9 = -4, etc.
%t A065870 nn=250;Module[{pr=Prime[Range[nn]],sp=Select[Range[nn],PrimeOmega[ #]==2&],len}, len=Min[nn,Length[sp]];#[[1]]-#[[2]]&/@ Thread[ {Take[ pr,len],Take[sp,len]}]](* _Harvey P. Dale_, Aug 14 2013 *)
%o A065870 (PARI) m=0; for (n=4, 250, if (bigomega(n) == 2, m = m + 1; print1(prime(m) - n,",")))
%o A065870 (PARI) n=m=0; for (k=1, 10^9, if (bigomega(k) != 2, next); m = m + 1; write("b065870.txt", n++, " ", prime(m) - k); if (n==1000, return) ) \\ _Harry J. Smith_, Nov 02 2009
%Y A065870 Cf. A000040, A001358, A038529 (n-th prime - n-th composite).
%K A065870 easy,sign
%O A065870 1,1
%A A065870 Robert A. Stump (bee_ess107(AT)yahoo.com), Dec 07 2001
%E A065870 More terms from _Rick L. Shepherd_, Mar 09 2002