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 A064141 #27 Mar 07 2025 02:56:14
%S A064141 0,0,0,0,0,12,0,0,72,328,0,768,1344,4032,3024,9072,0,36288,0,120960,
%T A064141 322560,967680,0,1935360,6013440,15966720,43545600,104094720,
%U A064141 163296000,362361600,149299200,447897600,1194393600,4644864000,2654208000
%N A064141 Sum of non-unitary divisors of central binomial coefficient C(n, floor(n/2)).
%H A064141 Amiram Eldar, <a href="/A064141/b064141.txt">Table of n, a(n) for n = 1..1000</a> (terms 1..200 from Harry J. Smith)
%F A064141 a(n) = A048146(A001405(n)). [corrected by _Amiram Eldar_, Mar 07 2025]
%F A064141 If n is in A046098 then a(n)=0.
%e A064141 For n = 6, binomial(6,3) = 20 = 4*5, divisors = {1,2,4,5,10,20} of which the non-unitary divisors are 2 and 10 with sum a(6) = 12.
%t A064141 nus[n_] := If[n==1, 0, DivisorSigma[1, n] - Times @@ (1 + Power @@@ FactorInteger[n])]; Table[nus@ Binomial[n, Floor[n/2]], {n, 35}] (* _Giovanni Resta_, Jun 22 2018 *)
%o A064141 (PARI) usigma(n)= { my(f,s=1); f=factor(n); for(i=1, matsize(f)[1], s*=1 + f[i, 1]^f[i, 2]); return(s) }
%o A064141 a(n)={my(b=binomial(n, n\2)); sigma(b) - usigma(b);} \\ _Harry J. Smith_, Sep 08 2009
%Y A064141 Cf. A034448, A001405, A046098, A048146, A048243.
%K A064141 nonn
%O A064141 1,6
%A A064141 _Labos Elemer_, Sep 11 2001