%I #19 Oct 18 2022 15:30:34
%S 1,5,12,23,39,61,90,127,173,229,296,375,467,573,694,831,985,1157,1348,
%T 1559,1791,2045,2322,2623,2949,3301,3680,4087,4523,4989,5486,6015,
%U 6577,7173,7804,8471,9175,9917,10698,11519,12381,13285,14232,15223,16259,17341,18470,19647
%N a(n) = (n^3 + 6*n^2 + 17*n + 6)/6.
%C a(1) = A339400(7) = A339400(11), a(2) = A339756(7) = A339756(11), a(3) = A339947(7) = A339947(11).
%C Conjecture: Mark each point on a 7^k or 11^k grid with the number of points that are visible from the point; for n > 0, a(n) is the number of distinct values in both grids.
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-6,4,-1).
%F a(n) = (n^3 + 6*n^2 + 17*n + 6)/6.
%F a(n) = A004006(n+2) - 2, n > 0.
%o (PARI) a(n) = (n^3 + 6*n^2 + 17*n + 6)/6;
%Y Cf. A004006, A339400, A339756, A339947.
%K nonn,easy
%O 0,2
%A _Torlach Rush_, Feb 06 2021