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a(n) = number of divisors of n^2 (excluding 1 and n^2).
4

%I #7 Nov 18 2019 17:12:49

%S 0,1,1,3,1,7,1,5,3,7,1,13,1,7,7,7,1,13,1,13,7,7,1,19,3,7,5,13,1,25,1,

%T 9,7,7,7,23,1,7,7,19,1,25,1,13,13,7,1,25,3,13,7,13,1,19,7,19,7,7,1,43,

%U 1,7,13,11,7,25,1,13,7,25,1,33,1,7,13,13,7,25,1,25,7,7,1,43,7,7,7,19,1,43,7

%N a(n) = number of divisors of n^2 (excluding 1 and n^2).

%H Harvey P. Dale, <a href="/A117677/b117677.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = A070824(n^2). - _Ray Chandler_, Nov 08 2018

%t Join[{0},DivisorSigma[0,Range[2,100]^2]-2] (* _Harvey P. Dale_, Oct 17 2016 *)

%Y Equals A048691(n) - 2 for n>1. Cf. A117679, A117010, A070824.

%K easy,nonn

%O 1,4

%A Mark Taggart (mt2612f(AT)aol.com), Apr 12 2006