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 A271606 #8 Aug 05 2019 06:37:29 %S A271606 1,0,1,1,1,1,1,1,1,1,0,2,1,1,1,0,1,2,0,1,1,0,0,3,0,1,0,2,0,1,2,2,1,0, %T A271606 0,1,0,1,1,1,0,3,0,1,0,0,0,3,0,2,0,0,0,2,0,2,1,0,0,3,0,1,1,0,1,0,0,1, %U A271606 0,0,0,5,1,1,0,0,0,1,0,2,0,1,0,3,1,0,0,0,0,3,2,0,1,0,0,4,0,2,0,0 %N A271606 Number of numbers k such that sigma_e(k) = n for some e > 0. %C A271606 We can't just define this as number of pairs k, e with e > 0 that have sigma_e(k) = n, because sigma_e(1) = 1 for all e. %H A271606 Amiram Eldar, <a href="/A271606/b271606.txt">Table of n, a(n) for n = 1..10000</a> %e A271606 a(28) = 2 because 28 = sigma_1(12) = 1+2+3+4+6+12 and also 28 = sigma_3(3) = 1^3+3^3. %o A271606 (PARI) alist(n)=my(r=vector(n),s);r[1]=1;for(k=2,n,e=1;while((s=sigma(k,e))<=n,r[s]++;e++));r %Y A271606 Cf. A054973, A109974. %K A271606 nonn %O A271606 1,12 %A A271606 _Franklin T. Adams-Watters_, Apr 10 2016