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A325848 Larger of exponentially-odd amicable numbers pair: numbers m < k such that m = s(k) and k = s(m), where s(k) is the sum of proper exponential-odd divisors of k. 2

%I #12 Sep 10 2019 21:43:30

%S 378,4584,16632,16728,64032,76704,179118,168730,225096,256338,266568,

%T 391656,401952,387720,393528,593952,788448,781728,897888,1052088,

%U 1099390,1292570,1346598,1598470,2062570,1863918,2099424,1940856,2223720,2429030,2980056,3336984

%N Larger of exponentially-odd amicable numbers pair: numbers m < k such that m = s(k) and k = s(m), where s(k) is the sum of proper exponential-odd divisors of k.

%C The terms are ordered according to their lesser counterparts (A325847).

%H Amiram Eldar, <a href="/A325848/b325848.txt">Table of n, a(n) for n = 1..789</a> (terms with lesser counterparts below 10^10)

%t f[e_] := If[OddQ[e], e + 2, e + 1]; fun[p_, e_] := 1 + (p^f[e] - p)/(p^2 - 1); a[1] = 1; a[n_] := Times @@ (fun @@@ (fct = FactorInteger[n])) - If[AllTrue[fct[[;; , 2]], OddQ], n, 0]; s = {}; Do[m = a[n]; If[m > n && a[m] == n, AppendTo[s, m]], {n, 1, 10^5}]; s

%Y Cf. A033289, A033634, A268335, A325847.

%K nonn

%O 1,1

%A _Amiram Eldar_, Sep 07 2019

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Last modified April 19 18:05 EDT 2024. Contains 371798 sequences. (Running on oeis4.)