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A099958 (1/2)*number of distinct angular positions under which an observer positioned at the center of an edge of a square lattice can see the (2n)X(2n-1) points symmetrically surrounding his position. 3

%I

%S 1,5,13,23,37,55,75,95,127,157,185,227,263,305,357,403,455,511,571,

%T 631,703,769,833,923,997,1069,1169,1245,1329,1443,1535,1631,1743,1849,

%U 1957,2075,2195,2307,2439,2565,2683,2845,2957,3097,3265,3385

%N (1/2)*number of distinct angular positions under which an observer positioned at the center of an edge of a square lattice can see the (2n)X(2n-1) points symmetrically surrounding his position.

%F This is a bisection of A049690, that is, a(n) = Sum[k=1..2n+1, phi(2k)]. - _Ralf Stephan_, Nov 13, 2004.

%Y See A099957 for further information. Cf. A049687, A049690, A190815.

%K nonn

%O 1,2

%A _Hugo Pfoertner_, Nov 13 2004

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Last modified May 21 02:57 EDT 2019. Contains 323434 sequences. (Running on oeis4.)