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Number of divisors of 7-smooth numbers.
2

%I #10 Jan 06 2020 08:36:29

%S 1,2,2,3,2,4,2,4,3,4,6,4,4,5,6,6,4,8,3,4,6,8,6,4,9,8,8,6,10,3,6,8,8,

%T 12,6,7,8,12,6,10,5,12,12,12,6,9,8,12,10,16,4,12,8,8,12,15,6,12,12,10,

%U 16,6,18,8,14,9,12,16,16,12,9,20,6,6,8,18,9,16,16,18,12,18,12,14

%N Number of divisors of 7-smooth numbers.

%H Amiram Eldar, <a href="/A086292/b086292.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A000005(A002473(n)).

%t DivisorSigma[0, Select[Range[500], Max[Transpose[FactorInteger[#]][[1]]] <= 7 &]] (* _Amiram Eldar_, Jan 06 2020 after G. C. Greubel at A086288 *)

%Y Cf. A000005, A002473, A086293.

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Jul 15 2003