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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. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The larger counterparts are in A333930.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..1000

EXAMPLE

220 is a terms since A333926(220) - 220 = 284 and A333926(284) - 284 = 220.

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

CROSSREFS

Cf. A333926, A333927, A333930.

Analogous sequences: A002025, A002952 (unitary), A126165 (exponential), A126169 (infinitary), A292980 (bi-unitary).

Sequence in context: A328063 A328065 A287011 * A157107 A175738 A260203

Adjacent sequences:  A333926 A333927 A333928 * A333930 A333931 A333932

KEYWORD

nonn

AUTHOR

Amiram Eldar, Apr 10 2020

STATUS

approved

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Last modified May 7 12:56 EDT 2021. Contains 343650 sequences. (Running on oeis4.)