The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A340715 Least positive number k such that sigma(k+1) = n * sigma(k). 2
 14, 5, 1, 37033919, 14182439039 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE n | sigma(a(n)) | sigma(a(n)+1) ----+-------------+--------------   1 |          24 |            24   2 |           6 |            12   3 |           1 |             3   4 |    39940992 |     159763968   5 | 14182439040 |   70912195200 MATHEMATICA 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 *) PROG (PARI) {a(n) = my(k=1); while(sigma(k+1)!=n*sigma(k), k++); k} CROSSREFS Cf. A000203, A002961, A058072, A067081, A077087, A080371, A340713, A340720. Sequence in context: A322776 A040186 A124600 * A344046 A084676 A180848 Adjacent sequences:  A340712 A340713 A340714 * A340716 A340717 A340718 KEYWORD nonn,hard,more AUTHOR Seiichi Manyama, Jan 17 2021 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 10 03:38 EDT 2022. Contains 356029 sequences. (Running on oeis4.)