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%I #31 Jan 08 2024 01:37:10
%S 0,0,0,0,1,1,1,1,1,2,1,2,1,2,2,2,1,3,1,3,2,2,1,4,2,2,2,3,1,5,1,3,2,2,
%T 3,5,1,2,2,5,1,5,1,3,4,2,1,6,2,4,2,3,1,5,3,5,2,2,1,8,1,2,4,4,3,5,1,3,
%U 2,6,1,8,1,2,4,3,3,5,1,7,3,2,1,8,3,2,2,5,1,9,3,3,2,2,3,8,1,4,4,6,1,5,1,5,6,2,1,8,1,6
%N Number of divisors of n which are greater than 4.
%H Seiichi Manyama, <a href="/A338648/b338648.txt">Table of n, a(n) for n = 1..10000</a>
%H <a href="/index/Di#divisors">Index entries for sequences related to divisors of numbers</a>.
%F G.f.: Sum_{k>=1} x^(5*k) / (1 - x^k).
%F L.g.f.: -log( Product_{k>=5} (1 - x^k)^(1/k) ).
%F a(n) = A000005(n) - A083040(n).
%F G.f.: Sum_{k>=5} x^k/(1 - x^k). - _Seiichi Manyama_, Jan 07 2023
%F Sum_{k=1..n} a(k) ~ n * (log(n) + 2*gamma - 37/12), where gamma is Euler's constant (A001620). - _Amiram Eldar_, Jan 08 2024
%t Table[DivisorSum[n, 1 &, # > 4 &], {n, 1, 110}]
%t nmax = 110; CoefficientList[Series[Sum[x^(5 k)/(1 - x^k), {k, 1, nmax}], {x, 0, nmax}], x] // Drop[#, 1] &
%t nmax = 110; CoefficientList[Series[-Log[Product[(1 - x^k)^(1/k), {k, 5, nmax}]], {x, 0, nmax}], x] Range[0, nmax] // Drop[#, 1] &
%o (PARI) a(n) = sumdiv(n, d, d>4); \\ _Michel Marcus_, Apr 22 2021; corrected Jun 13 2022
%o (PARI) my(N=100, x='x+O('x^N)); concat([0, 0, 0, 0], Vec(sum(k=5, N, x^k/(1-x^k)))) \\ _Seiichi Manyama_, Jan 07 2023
%Y Column k=5 of A135539.
%Y Cf. A000005, A001620, A023645, A032741, A083040, A321014, A338649, A338650, A338651, A338652, A338653.
%K nonn,easy
%O 1,10
%A _Ilya Gutkovskiy_, Apr 22 2021
%E a(1)-a(4) prepended by _David A. Corneth_, Jun 13 2022
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