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 A107753 #2 Mar 30 2012 17:22:40 %S A107753 1,2,2,3,2,6,2,5,4,8,2,11,2,10,9,9,2,16,2,15,11,14,2,21,6,16,10,19,2, %T A107753 212,2,17,15,20,13,31,2,22,17,29,2 %N A107753 Number of primitive subsets of the n-th roots of unity summing to zero. %C A107753 A primitive subset has no nonempty proper subset whose members sum to zero. Note that a(30) is the first term for which the formulas do not apply. For n=30, there are 1,0,15,10,0,5,30,60,60,30 primitive subsets of size 0,1,2,...,9. %F A107753 For primes p and q, if n = p^i, then a(n)=1+n/p; if n=p^i q^j, then a(n)=1+n/p+n/q. %Y A107753 Cf. A103314 (number of subsets of the n-th roots of unity summing to zero), A107754 (number of subsets of the n-th roots of unity summing to one). %K A107753 nonn %O A107753 1,2 %A A107753 _T. D. Noe_, May 23 2005