A180813 - OEIS

%I #6 Jun 02 2025 03:07:46

%S 0,0,1,0,2,2,0,4,7,2,0,6,18,12,3,0,9,42,50,24,2,0,12,84,166,136,31,4,

%T 0,16,153,474,612,262,59,4,0,20,264,1200,2325,1649,583,74,4,0,25,429,

%U 2768,7752,8468,4501,974,111,3,0,30,666,5920,23256,37264,28778,9772,1794,121

%N T(n,k)=number of distinct solutions of sum{i=1..k}(x(2i-1)*x(2i)) = 1 (mod n), with x() in 0..n-1.

%C Table starts

%C .0...0....0.....0......0.......0........0.........0..........0...........0

%C .1...2....4.....6......9......12.......16........20.........25..........30

%C .2...7...18....42.....84.....153......264.......429........666........1001

%C .2..12...50...166....474....1200.....2768......5920......11900.......22696

%C .3..24..136...612...2325....7752....23256.....63954.....163438......392250

%C .2..31..262..1649...8468...37264...145098....510927....1652886.....4972016

%C .4..59..583..4501..28778..158239...768537...3362288...13449080....49761505

%C .4..74..974..9772..79670..550860..3329262..17975676...88130750...397307654

%C .4.111.1794.21631.212049.1766580.12867751..83628636..492442470..2659084116

%C .3.121.2603.39911.484180.4912624.43149935.335900991.2357340087.15109820870

%H R. H. Hardin, <a href="/A180813/b180813.txt">Table of n, a(n) for n=1..2016</a>

%K nonn,tabl

%O 1,5

%A _R. H. Hardin_, suggested by _Max Alekseyev_ in the Sequence Fans Mailing List, Sep 20 2010