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 A180791 #5 Jun 02 2025 03:05:52
%S A180791 0,1,18,502,9721,135902,1430707,11752870,78770466,442714845,
%T A180791 2151608163,9202214058,35373572486,123540794708,398005342048,
%U A180791 1190430659772,3344070542314,8854626554163,22304900540858,53543330420874
%N A180791 Number of distinct solutions of sum{i=1..9}(x(2i-1)*x(2i)) = 1 (mod n), with x() only in 1..n-1.
%C A180791 Column 9 of A180793
%H A180791 R. H. Hardin, <a href="/A180791/b180791.txt">Table of n, a(n) for n=1..183</a>
%e A180791 Solutions for sum of products of 9 1..2 pairs = 1 (mod 3) are
%e A180791 (1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 1*2)
%e A180791 (1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 1*2 + 2*2)
%e A180791 (1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 1*2 + 2*2 + 2*2)
%e A180791 (1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 1*2 + 1*2 + 1*2 + 1*2)
%e A180791 (1*1 + 1*1 + 1*1 + 1*1 + 1*2 + 1*2 + 1*2 + 1*2 + 2*2)
%e A180791 (1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 1*2 + 2*2 + 2*2 + 2*2)
%e A180791 (1*1 + 1*1 + 1*1 + 1*1 + 1*2 + 2*2 + 2*2 + 2*2 + 2*2)
%e A180791 (1*1 + 1*1 + 1*1 + 1*2 + 1*2 + 1*2 + 1*2 + 2*2 + 2*2)
%e A180791 (1*1 + 1*1 + 1*1 + 1*2 + 2*2 + 2*2 + 2*2 + 2*2 + 2*2)
%e A180791 (1*1 + 1*1 + 1*2 + 1*2 + 1*2 + 1*2 + 1*2 + 1*2 + 1*2)
%e A180791 (1*1 + 1*1 + 1*2 + 1*2 + 1*2 + 1*2 + 2*2 + 2*2 + 2*2)
%e A180791 (1*1 + 1*1 + 1*2 + 2*2 + 2*2 + 2*2 + 2*2 + 2*2 + 2*2)
%e A180791 (1*1 + 1*2 + 1*2 + 1*2 + 1*2 + 1*2 + 1*2 + 1*2 + 2*2)
%e A180791 (1*1 + 1*2 + 1*2 + 1*2 + 1*2 + 2*2 + 2*2 + 2*2 + 2*2)
%e A180791 (1*1 + 1*2 + 2*2 + 2*2 + 2*2 + 2*2 + 2*2 + 2*2 + 2*2)
%e A180791 (1*2 + 1*2 + 1*2 + 1*2 + 1*2 + 1*2 + 1*2 + 2*2 + 2*2)
%e A180791 (1*2 + 1*2 + 1*2 + 1*2 + 2*2 + 2*2 + 2*2 + 2*2 + 2*2)
%e A180791 (1*2 + 2*2 + 2*2 + 2*2 + 2*2 + 2*2 + 2*2 + 2*2 + 2*2)
%K A180791 nonn
%O A180791 1,3
%A A180791 _R. H. Hardin_ Sep 20 2010