This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A348271 #11 Feb 16 2025 08:34:02
%S A348271 0,0,0,2,0,0,0,0,3,0,0,8,0,0,0,14,0,9,0,12,0,0,0,0,5,0,0,16,0,0,0,12,
%T A348271 0,0,0,41,0,0,0,0,0,0,0,24,18,0,0,56,7,15,0,28,0,0,0,0,0,0,0,48,0,0,
%U A348271 24,42,0,0,0,36,0,0,0,45,0,0,20,40,0,0,0,84,39
%N A348271 a(n) is the sum of noninfinitary divisors of n.
%H A348271 Amiram Eldar, <a href="/A348271/b348271.txt">Table of n, a(n) for n = 1..10000</a>
%H A348271 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/InfinitaryDivisor.html">Infinitary Divisor</a>.
%F A348271 a(n) = A000203(n) - A049417(n).
%F A348271 a(n) = 0 if and only if the number of divisors of n is a power of 2, (i.e., n is in A036537).
%F A348271 a(n) > 0 if and only if the number of divisors of n is not a power of 2, (i.e., n is in A162643).
%e A348271 a(12) = 8 since 12 has 2 noninfinitary divisors, 2 and 6, and 2 + 6 = 8.
%t A348271 f[p_, e_] := Module[{b = IntegerDigits[e, 2], m}, m = Length[b]; Product[If[b[[j]] > 0, 1 + p^(2^(m - j)), 1], {j, 1, m}]]; isigma[1] = 1; isigma[n_] := Times @@ f @@@ FactorInteger[n]; a[n_]:= DivisorSigma[1,n] - isigma[n]; Array[a, 100]
%Y A348271 Cf. A000203, A036537, A049417, A077609, A162643, A327633.
%Y A348271 Similar sequences: A034448, A048146, A051377, A188999.
%K A348271 nonn
%O A348271 1,4
%A A348271 _Amiram Eldar_, Oct 09 2021