A333929 Lesser of recursive amicable numbers pair: numbers m < k such that m = s(k) and k = s(m), where s(k) = A333926(k) - k is the sum of proper recursive divisors of k.
220, 366, 2620, 3864, 5020, 16104, 16536, 26448, 29760, 43524, 63020, 67344, 69615, 100485, 122265, 142290, 142310, 196248, 196724, 198990, 239856, 240312, 280540, 308620, 309264, 319550, 326424, 341904, 348840, 366792, 469028, 522405, 537744, 580320, 647190, 661776
Offset: 1
Keywords
Examples
220 is a terms since A333926(220) - 220 = 284 and A333926(284) - 284 = 220.
Links
- Amiram Eldar, Table of n, a(n) for n = 1..1000
Crossrefs
Programs
-
Mathematica
recDivQ[n_, 1] = True; recDivQ[n_, d_] := recDivQ[n, d] = Divisible[n, d] && AllTrue[FactorInteger[d], recDivQ[IntegerExponent[n, First[#]], Last[#]] &]; recDivs[n_] := Select[Divisors[n], recDivQ[n, #] &]; f[p_, e_] := 1 + Total[p^recDivs[e]]; recDivSum[1] = 1; recDivSum[n_] := Times @@ (f @@@ FactorInteger[n]); s[n_] := recDivSum[n] - n; seq = {}; Do[m = s[n]; If[m > n && s[m] == n, AppendTo[seq, n]], {n, 1, 10^5}]; seq
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