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%I #18 Jan 19 2019 21:05:40
%S 1,1,1,1,1,2,1,2,1,2,1,4,1,2,2,3,1,4,1,4,2,2,1,6,1,2,2,4,1,6,1,4,2,2,
%T 2,7,1,2,2,6,1,6,1,4,4,2,1,8,1,4,2,4,1,6,2,6,2,2,1,10,1,2,4,5,2,6,1,4,
%U 2,6,1,10,1,2,4,4,2,6,1,8
%N Row lengths of the irregular triangle A137510 (number of divisors d of n with 1 < d < n, or 0 if no such d exists).
%C See A032741 for the number of divisors d of n with 1 <= d < n, n >= 1.
%C See A070824 for the number of the divisors d of n with 1 < d < n, n >= 1.
%H Antti Karttunen, <a href="/A264440/b264440.txt">Table of n, a(n) for n = 1..10000</a>
%F a(1) = 1; a(n) = 1 if n is prime, otherwise a(n) = A070824(n).
%F a(1) = 1; a(n) = 1 if n is prime, otherwise a(n) = A032741(n) - 1.
%F a(n) = max(1, A000005(n)-2). - _Robert Israel_, Jan 20 2016
%p seq(max(1,numtheory:-tau(n)-2), n=1..100); # _Robert Israel_, Jan 20 2016
%t Array[DivisorSigma[0, #] - 2 &, {80}] /. n_ /; n < 2 -> 1 (* _Michael De Vlieger_, Jan 16 2016 *)
%o (PARI) A264440(n) = max(1,numdiv(n)-2); \\ After _Robert Israel_'s formula. - _Antti Karttunen_, May 25 2017
%Y Cf. A000005, A000040, A032741, A070824, A137510.
%K nonn,easy
%O 1,6
%A _Wolfdieter Lang_, Jan 16 2016
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