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A340720 Least positive number k such that sigma(k) = n * sigma(k+1). 2
14, 12, 180, 25908120 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..4.

EXAMPLE

  n | sigma(a(n)) | sigma(a(n)+1)

----+-------------+--------------

  1 |          24 |            24

  2 |          28 |            14

  3 |         546 |           182

  4 |   103680000 |      25920000

PROG

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

CROSSREFS

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

Sequence in context: A206605 A004503 A140810 * A166041 A335170 A115019

Adjacent sequences:  A340717 A340718 A340719 * A340721 A340722 A340723

KEYWORD

nonn,more,hard

AUTHOR

Seiichi Manyama, Jan 17 2021

STATUS

approved

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Last modified June 28 12:00 EDT 2022. Contains 354907 sequences. (Running on oeis4.)