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a(n) is the number of different pairs (p,q) mod n not of the form (x*y,x+y) mod n for any (x,y).
1

%I #15 Sep 19 2015 13:20:04

%S 0,1,3,8,10,18,21,36,45,55,55,96,78,112,135,160,136,216,171,280,273,

%T 286,253,408,350,403,432,560,406,630,465,656,693,697,805,1008,666,874,

%U 975,1180,820,1260,903,1408,1485,1288,1081,1728,1323,1675,1683,1976,1378,2025,2035,2352,2109,2059,1711,2880,1830,2356

%N a(n) is the number of different pairs (p,q) mod n not of the form (x*y,x+y) mod n for any (x,y).

%F a(n) = n^2 - A261928(n).

%e a(2) = 1 because only the pair (1,1) mod 2 doesn't exist as result from any (x*y,x+y) mod 2.

%Y Cf. A261928 (number of pairs that have such a form).

%K nonn

%O 1,3

%A _Thomas Kerscher_, Sep 06 2015