login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 5000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".

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 | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified December 7 20:56 EST 2016. Contains 278895 sequences.