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1,2
Table of n, a(n) for n=1..4.
A000005(a(n)) = a(n-1) + 4 for n >= 2.
a(3) = 240 = the smallest number with 16 + 4 = 20 divisors.
Cf. A014221, A175718, A175719.
Sequence in context: A005619 A204793 A173605 * A135518 A179092 A231020
Adjacent sequences: A175717 A175718 A175719 * A175721 A175722 A175723
nonn
Jaroslav Krizek, Aug 15 2010
approved