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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
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
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

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Last modified February 26 07:39 EST 2024. Contains 370335 sequences. (Running on oeis4.)