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 A089646 #3 Mar 30 2012 18:50:42 %S A089646 1,1,2,2,3,4,5,5,6,7,8,9,10,11,13,13,14,16,17,18,20,21,22,23,24,25,26, %T A089646 27,28,32,33,33,35,36,38,41,42,43,45,46,47,51,52,53,56,57,58,59,60,62, %U A089646 64,65,66,69,71,72,74,75,76,82,83,84,87,87,89,93,94,95,97,101,102,106 %N A089646 a(n) = Sum(a(floor(n/p)): p prime and p<=n); a(1) = 1. %e A089646 a(10) = a([10/2])+a([10/3])+a([10/5])+a([10/7]) = %e A089646 a(5)+a(3)+a(2)+a(1) = (a([5/2])+a([5/3])+a([5/5])) + (a([3/2])+a([3/3])) + %e A089646 a([2/2]) + a(1) = (a(2)+a(1)+a(1)) + (a(1)+a(1)) + a(1) + a(1) = a([2/2]) + %e A089646 6*a(1) = a(1) + 6*1 = 7. %Y A089646 Cf. A022825. %K A089646 nonn %O A089646 1,3 %A A089646 _Reinhard Zumkeller_, Jan 02 2004