A362936 a(n) = A000982(n) - A362931(n).

0, 0, 2, 4, 8, 8, 14, 20, 28, 36, 46, 52, 64, 76, 86, 100, 116, 128, 146, 160, 180, 200, 222, 240, 264, 288, 314, 336, 364, 384, 414, 444, 476, 508, 538, 568, 604, 640, 678, 712, 752, 784, 826, 868, 904, 948, 994, 1036, 1084, 1132, 1182, 1232, 1284, 1332, 1386, 1436, 1492, 1548, 1606, 1652, 1712

Offset: 1

Author

N. J. A. Sloane, Aug 28 2023

Keywords

• nonn

Comments

a(n) = (number of pairs (i,j) in [1..n] X [1..n] with integral arithmetic mean) - (number of pairs (i,j) in [1..n] X [1..n] with integral harmonic mean).

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000982, A132188, A362931-A932937.

Programs

Python

def A362936(n): return ((n-1)**2>>1)-(sum(1 for x in range(1,n+1) for y in range(1,x) if not (x*y<<1)%(x+y))<<1) # Chai Wah Wu, Aug 29 2023