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%I #50 Jan 06 2022 05:17:08
%S 2,3,3,4,3,5,3,5,4,5,3,7,3,5,5,6,3,7,3,7,5,5,3,9,4,5,5,7,3,9,3,7,5,5,
%T 5,10,3,5,5,9,3,9,3,7,7,5,3,11,4,7,5,7,3,9,5,9,5,5,3,13,3,5,7,8,5,9,3,
%U 7,5,9,3,13,3,5,7,7,5,9,3,11,6,5,3,13,5,5,5,9,3,13,5,7,5,5,5,13,3,7,7,10,3,9,3,9
%N a(n) is 1 plus the number of divisors of n.
%C a(n) is the number of times that every divisor of n occurs in the coordinates of divisors of n mentioned in A337360 (Corneth).
%C a(n) = 3 if and only if n is prime.
%C a(n) is even if and only if n is a square.
%C a(n) is the number of characteristic subgroups of the dihedral group D_2n. - _Firdous Ahmad Mala_, Dec 25 2021
%H David A. Corneth, <a href="/A334954/b334954.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = 1 + A000005(n).
%F a(n) = A337360(n)/A000203(n).
%F a(n) = A212356(n) for n >= 3. - _Ilya Gutkovskiy_, Aug 27 2020
%t 1 + DivisorSigma[0, Range[105]] (* _Michael De Vlieger_, Sep 11 2020 *)
%o (PARI) a(n) = numdiv(n) + 1
%Y Partial sums give A156745.
%Y Cf. A000005, A088580, A000203, A212356, A337360.
%K nonn,easy
%O 1,1
%A _David A. Corneth_ and _Omar E. Pol_, Aug 25 2020
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