cp's OEIS Frontend

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.

%I A266115 #9 Dec 23 2015 14:11:54
%S A266115 2,4,10,12,15,16,21,26,28,30,33,36,39,42,45,48,52,54,55,60,63,64,66,
%T A266115 69,70,75,76,78,80,85,90,91,100,108,110,111,112,115,117,122,124,126,
%U A266115 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
%N 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.
%C A266115 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).
%H A266115 Antti Karttunen, <a href="/A266115/b266115.txt">Table of n, a(n) for n = 1..10000</a>
%e A266115 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.
%o A266115 (Scheme, with _Antti Karttunen_'s IntSeq-library)
%o A266115 (define A266115 (ZERO-POS 1 1 A266112))
%Y A266115 Cf. A000005, A082284, A263267, A266112.
%Y A266115 Cf. A266114 (complement).
%K A266115 nonn
%O A266115 1,1
%A A266115 _Antti Karttunen_, Dec 21 2015