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 A093321 #10 Mar 28 2015 22:16:11
%S A093321 1,0,1,0,1,1,2,1,2,0,2,2,3,3,3,3,4,5,6,5,7,5,7,8,8,7,9,8,9,7,9,10,10,
%T A093321 8,10,10,11,11,12,11,13,15,16,17,18,16,19,21,22,20,20,20,22,24,23,24,
%U A093321 24,24,25,27,29,31,34,33,32,32,34,37,38,38,40,44,45,49,51,50,51,50,52,55
%N A093321 a(1) = 1; for m >= 2, a(m) =sum_{primes p<m which do not divide m} a(pi(p)), where pi(p) is the order of p among the primes = the number of primes <= p.
%t A093321 PrimeFactors[n_Integer] := Flatten[ Table[ # [[1]], {1}] & /@ FactorInteger[n]]; a[1] = 1; a[n_] := a[n] = (Plus @@ (a[ # ] & /@ Complement[ Range[ PrimePi[n]], PrimePi[ PrimeFactors[n]]])); Table[ a[n], {n, 80}] (* _Robert G. Wilson v_, May 04 2004 *)
%Y A093321 Cf. A093320, A094163.
%K A093321 nonn,easy
%O A093321 1,7
%A A093321 _Leroy Quet_, Apr 26 2004
%E A093321 More terms from _Robert G. Wilson v_, May 04 2004