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 A266875 #8 Jan 09 2016 19:35:27
%S A266875 0,1,1,3,1,3,1,3,1,3,1,3,1,3,4,3,1,9,1
%N A266875 Number of partially ordered sets ("posets") with n labeled elements, modulo n.
%C A266875 If n is a prime number, a(n) = 1 because of the fact that A001035(p^k) == 1 mod p for all primes p.
%C A266875 If n is an even number, a(n) is a number of the form 3^k for n <= 19. How is the distribution of terms of the form 3^k in this sequence?
%F A266875 a(n) = A001035(n) mod n, for n > 0.
%F A266875 a(A000040(n)) = A265847(A000040(n)) - 1, for n > 1.
%e A266875 a(4) = A001035(4) mod 4 = 219 mod 4 = 3.
%e A266875 a(5) = A001035(5) mod 5 = 4231 mod 5 = 1.
%e A266875 a(6) = A001035(6) mod 6 = 130023 mod 6 = 3.
%e A266875 a(7) = A001035(7) mod 7 = 6129859 mod 7 = 1.
%Y A266875 Cf. A001035, A265847.
%K A266875 nonn,more
%O A266875 1,4
%A A266875 _Altug Alkan_, Jan 05 2016