A340715 -id:A340715 - cp's OEIS frontend

A340713 Numbers k such that sigma(k+1) = 4 * sigma(k).

37033919, 141162839, 264995639, 596672999, 606523679, 630777839, 791656319, 920424119, 1060332839, 1379454719, 1954690919, 3799661039, 4024838999, 4633959959, 5393988599, 5935994063, 8831231639, 9866482079, 11237657759, 11273710139, 12266364599, 14440498379, 14952625379

Offset: 1

Seiichi Manyama, Jan 17 2021

nonn

Seiichi Manyama, Table of n, a(n) for n = 1..40 (using A058072 data)

Cf. A000203, A002961, A058072, A067081, A077087, A340715.

isok(k) = sigma(k+1) == 4*sigma(k); \\ Michel Marcus, Jan 18 2021

a(10)-a(23) from Seiichi Manyama using A058072 data, Jan 17 2021

A340720 Least positive number k such that sigma(k) = n * sigma(k+1).

Original entry on oeis.org

14, 12, 180, 25908120

Offset: 1

Seiichi Manyama, Jan 17 2021

			  n | sigma(a(n)) | sigma(a(n)+1)
----+-------------+--------------
  1 |          24 |            24
  2 |          28 |            14
  3 |         546 |           182
  4 |   103680000 |      25920000

Cf. A002961, A080372, A163193, A217791, A340715.

{a(n) = my(k=1); while(sigma(k)!=n*sigma(k+1), k++); k}

cp's OEIS Frontend

A340713 Numbers k such that sigma(k+1) = 4 * sigma(k).

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