A266115 Numbers which have smaller siblings in A263267-tree: numbers n for which there exists some k < n such that k - d(k) = n - d(n), where d(n) = A000005(n), the number of divisors of n.

2, 4, 10, 12, 15, 16, 21, 26, 28, 30, 33, 36, 39, 42, 45, 48, 52, 54, 55, 60, 63, 64, 66, 69, 70, 75, 76, 78, 80, 85, 90, 91, 100, 108, 110, 111, 112, 115, 117, 122, 124, 126, 129, 132, 133, 138, 140, 141, 144, 147, 148, 150, 153, 156, 159, 165, 168, 170, 171, 172, 174, 176, 180, 182, 183, 189, 190, 192, 196, 201, 207, 208, 213, 222

Offset: 1

Author

Antti Karttunen, Dec 21 2015

Keywords

• nonn

Comments

At least initially, the majority of the odd squares (A016754) seem to be in A266114, while the majority of the even squares (A016742) seem to be in A266115. The first exceptions to this are 63^2 = 3969 = A266115(1296), and 20^2 = 400 = A266114(269).

Examples

			2 is present, as 2 - A000005(2) = 0, but also 1 - A000005(1) = 0, thus 1 is a smaller sibling of 2 in a tree A263267 defined by edge-relation child - A000005(child) = parent.
		

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000005, A082284, A263267, A266112.

Cf. A266114 (complement).