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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A074242 Numbers n such that sigma(n+1) = reverse(sigma(n)). 1
 5602, 42346, 184650339, 356930335, 453038125082 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(6) > 10^13. - Giovanni Resta, Jun 26 2015 LINKS Table of n, a(n) for n=1..5. EXAMPLE sigma(5602 + 1) = 6048 = reverse(8406) = reverse(sigma(5602)), so 5602 is a term of the sequence. MATHEMATICA Do[ If[FromDigits[Reverse[IntegerDigits[DivisorSigma[1, n]]]] == DivisorSigma[1, n + 1], Print[n]], {n, 1, 10^7}] PROG (PARI) isok(n) = digits(sigma(n+1)) == Vecrev(digits(sigma(n))); \\ Michel Marcus, Jun 26 2015 CROSSREFS Cf. A028980 (sigma(n) = reverse(sigma(n))). Sequence in context: A109565 A126784 A071813 * A032737 A237507 A198164 Adjacent sequences: A074239 A074240 A074241 * A074243 A074244 A074245 KEYWORD base,more,nonn AUTHOR Joseph L. Pe, Sep 19 2002 EXTENSIONS a(3)-a(4) from Donovan Johnson, Feb 01 2009 a(5) from Giovanni Resta, Jun 26 2015 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 February 26 07:39 EST 2024. Contains 370335 sequences. (Running on oeis4.)