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.

1, 5, 13, 23, 37, 55, 75, 95, 127, 157, 185, 227, 263, 305, 357, 403, 455, 511, 571, 631, 703, 769, 833, 923, 997, 1069, 1169, 1245, 1329, 1443, 1535, 1631, 1743, 1849, 1957, 2075, 2195, 2307, 2439, 2565, 2683, 2845, 2957, 3097, 3265, 3385

Offset: 1

Author

Hugo Pfoertner, Nov 13 2004

Keywords

• nonn

Crossrefs

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

Formula

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