A275018 - OEIS

%I #39 Jun 11 2024 15:45:17

%S 0,0,0,0,0,1,1,5,6,10,11,19,20,29,33,38,43,56,60,76,81,90,98,118,121,

%T 138,147,163,172,197,202,230,243,260,273,294,303,336,352,373,384,421,

%U 430,470,487,508,528,572,583,623,640

%N a(n) = A278846(n)/8.

%H Indranil Ghosh and Chai Wah Wu, <a href="/A275018/b275018.txt">Table of n, a(n) for n = 0..10000</a> (terms n = 0..200 from Indranil Ghosh)

%o (Python)

%o def a(n):

%o     s=0

%o     for a in range(0, n+1):

%o         for b in range(0, n+1):

%o             for c in range(0, n+1):

%o                 for d in range(0, n+1):

%o                     if (a!=b  and a!=d and b!=d and c!=a and c!=b and c!=d):

%o                         if abs(a*d-b*c)==1:

%o                             s+=1

%o     return s

%o print([int(a(n)/8) for n in range(0, 52)]) # _Indranil Ghosh_, Nov 30 2016

%Y Cf. A278846.

%K nonn

%O 0,8

%A _Indranil Ghosh_, Nov 30 2016