cp's OEIS Frontend

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).

%I A322542 #11 Dec 18 2018 11:29:41
%S A322542 126,378,1260,3780,4584,5544,11424,15390,16632,16728,25296,49308,
%T A322542 68760,73962,88608,84336,179118,168730,172560,225096,256338,266568,
%U A322542 250920,297024,287280,365700,374304,391656,374418,387720,386568,393528,548550,502656,623280
%N 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).
%C A322542 The terms are ordered according to the order of their lesser counterparts (A322541).
%e A322542 126 is in the sequence since it is the larger of the amicable pair (114, 126): susigma(114) = susigma(126) = 114 + 126.
%t A322542 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 A322542 (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 A322542 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 A322542 Cf. A002025, A002952, A322485, A322486, A322541.
%K A322542 nonn
%O A322542 1,1
%A A322542 _Amiram Eldar_, Dec 14 2018