

A266115


Numbers which have smaller siblings in A263267tree: 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.


4



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
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OFFSET

1,1


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).


LINKS

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


EXAMPLE

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 edgerelation child  A000005(child) = parent.


PROG

(Scheme, with Antti Karttunen's IntSeqlibrary)
(define A266115 (ZEROPOS 1 1 A266112))


CROSSREFS

Cf. A000005, A082284, A263267, A266112.
Cf. A266114 (complement).
Sequence in context: A138940 A278465 A129412 * A113536 A081887 A085344
Adjacent sequences: A266112 A266113 A266114 * A266116 A266117 A266118


KEYWORD

nonn


AUTHOR

Antti Karttunen, Dec 21 2015


STATUS

approved



