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A322542 Larger of semi-unitary amicable numbers pair: numbers (m, n) such that susigma(m) = susigma(n) = m + n, where susigma(n) is the sum of the semi-unitary divisors of n (A322485). 2

%I

%S 126,378,1260,3780,4584,5544,11424,15390,16632,16728,25296,49308,

%T 68760,73962,88608,84336,179118,168730,172560,225096,256338,266568,

%U 250920,297024,287280,365700,374304,391656,374418,387720,386568,393528,548550,502656,623280

%N Larger of semi-unitary amicable numbers pair: numbers (m, n) such that susigma(m) = susigma(n) = m + n, where susigma(n) is the sum of the semi-unitary divisors of n (A322485).

%C The terms are ordered according to the order of their lesser counterparts (A322541).

%e 126 is in the sequence since it is the larger of the amicable pair (114, 126): susigma(114) = susigma(126) = 114 + 126.

%t f[p_, e_] := (p^Floor[(e + 1)/2] - 1)/(p - 1) + p^e; s[n_] := If[n == 1, 1, Times @@ (f @@@ FactorInteger[n])] - n; seq = {}; Do[n = s[m]; If[n > m && s[n] == m, AppendTo[seq, n]], {m, 1, 1000000}]; seq

%o (PARI) susigma(n) = {my(f = factor(n)); for (k=1, #f~, my(p=f[k, 1], e=f[k, 2]); f[k, 1] = (p^((e+1)\2) - 1)/(p-1) + p^e; f[k, 2] = 1; ); factorback(f); } \\ A322485

%o lista(nn) = {for (n=1, nn, my(m=susigma(n)-n); if ((m > n) && (susigma(m) == n + m), print1(m, ", ")););} \\ _Michel Marcus_, Dec 15 2018

%Y Cf. A002025, A002952, A322485, A322486, A322541.

%K nonn

%O 1,1

%A _Amiram Eldar_, Dec 14 2018

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Last modified July 21 04:40 EDT 2019. Contains 325189 sequences. (Running on oeis4.)