cp's OEIS Frontend

A134322 Positive integers with fewer non-isolated divisors than isolated divisors. A divisor, k, of n is non-isolated if (k-1) or (k+1) also divides n. A divisor, k, of n is isolated if neither (k-1) nor (k+1) divides n.

%I A134322 #8 Apr 09 2014 10:16:33
%S A134322 1,3,5,7,9,11,13,15,16,17,19,21,23,25,27,28,29,31,32,33,35,36,37,39,
%T A134322 41,43,44,45,47,48,49,50,51,52,53,54,55,57,59,61,63,64,65,66,67,68,69,
%U A134322 70,71,73,75,76,77,78,79,80,81,83,85,87,88,89,91,92,93,95,96,97,98,99,100
%N A134322 Positive integers with fewer non-isolated divisors than isolated divisors. A divisor, k, of n is non-isolated if (k-1) or (k+1) also divides n. A divisor, k, of n is isolated if neither (k-1) nor (k+1) divides n.
%C A134322 All odd positive integers are in the sequence, since every divisor of any odd number is isolated.
%e A134322 The divisors of 50 are 1,2,5,10,25,50. Of these, 1 and 2 are non-isolated divisors and 5,10,25,50 are isolated divisors. There are fewer non-isolated divisors (2 in number) than isolated divisors (4 in number), so 50 is in the sequence.
%Y A134322 Cf. A134320, A134321.
%K A134322 nonn
%O A134322 1,2
%A A134322 _Leroy Quet_, Oct 20 2007
%E A134322 Extended by _Ray Chandler_, Jun 24 2008