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%I #24 Jan 17 2021 10:57:17
%S 14,5,1,37033919,14182439039
%N Least positive number k such that sigma(k+1) = n * sigma(k).
%e n | sigma(a(n)) | sigma(a(n)+1)
%e ----+-------------+--------------
%e 1 | 24 | 24
%e 2 | 6 | 12
%e 3 | 1 | 3
%e 4 | 39940992 | 159763968
%e 5 | 14182439040 | 70912195200
%t k = 1;n = 1;Print[While[DivisorSigma[1, k + 1] != n*DivisorSigma[1, k], k;k k+]; k] (* _Robert P. P. McKone_, Jan 17 2021 *)
%o (PARI) {a(n) = my(k=1); while(sigma(k+1)!=n*sigma(k), k++); k}
%Y Cf. A000203, A002961, A058072, A067081, A077087, A080371, A340713, A340720.
%K nonn,hard,more
%O 1,1
%A _Seiichi Manyama_, Jan 17 2021
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