A362937 a(n) = (A000982(n) - A362931(n))/2.

0, 0, 1, 2, 4, 4, 7, 10, 14, 18, 23, 26, 32, 38, 43, 50, 58, 64, 73, 80, 90, 100, 111, 120, 132, 144, 157, 168, 182, 192, 207, 222, 238, 254, 269, 284, 302, 320, 339, 356, 376, 392, 413, 434, 452, 474, 497, 518, 542, 566, 591, 616, 642, 666, 693, 718, 746, 774, 803, 826, 856, 886, 915, 946, 978

Offset: 1

Author

N. J. A. Sloane, Aug 28 2023

Keywords

• nonn

Comments

a(n) = one-half of (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, A362931-A362936.

Programs

Python

def A362937(n): return ((n-1)**2>>2)-sum(1 for x in range(1,n+1) for y in range(1,x) if not (x*y<<1)%(x+y)) # Chai Wah Wu, Aug 29 2023