cp's OEIS Frontend

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.

A339983 Coreful abundant numbers (A308053) with an even sum of coreful divisors (A057723) that are not coreful Zumkeller numbers (A339979).

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%I A339983 #5 Dec 25 2020 19:32:56
%S A339983 108,216,432,540,756,864,972,1000,1080,1188,1404,1512,1728,1836,1944,
%T A339983 2000,2052,2160,2376,2484,2744,2808,3000,3024,3132,3348,3456,3672,
%U A339983 3780,3888,3996,4000,4104,4320,4428,4644,4752,4860,4968,5076,5488,5616,5724,5940,6000
%N A339983 Coreful abundant numbers (A308053) with an even sum of coreful divisors (A057723) that are not coreful Zumkeller numbers (A339979).
%e A339983 108 is a term since its set of coreful divisors, {6, 12, 18, 36, 54, 108}, has an even sum, 234 > 2*108, and it cannot be partitioned into two disjoint sets of equal sum.
%t A339983 q[n_] := Module[{r = Times @@ FactorInteger[n][[;; , 1]], d, sum, x}, d = r*Divisors[n/r]; (sum = Plus @@ d) >= 2*n && EvenQ[sum] && CoefficientList[Product[1 + x^i, {i, d}], x][[1 + sum/2]] == 0]; Select[Range[10^4], q]
%Y A339983 Subsequence of A308053.
%Y A339983 Cf. A057723, A339979, A339982.
%Y A339983 Similar sequences: A171641, A323341, A323342, A323343, A323344.
%K A339983 nonn
%O A339983 1,1
%A A339983 _Amiram Eldar_, Dec 25 2020