A115892 Numbers k such that sigma(k)*phi(k) is a palindrome.

1, 2, 3, 69, 219, 221, 224, 254, 1772, 2181, 15463, 50807, 63551, 94236, 161257, 602962, 2105689, 8371756, 2115856505, 2539027806, 5472276593, 6819131191, 15442198064, 16190055003, 46870943027

Offset

1,2

Comments

a(26) > 5*10^10. 205447718981 is also a term. - Donovan Johnson, Sep 30 2011

Links

Table of n, a(n) for n=1..25.

Example

sigma(15463)*phi(15463) = 18056*12972 = 234222432.

Crossrefs

Cf. A084122, A115890, A115891.

Sequence in context: A132598 A257173 A232618 * A290329 A145531 A140546

Adjacent sequences: A115889 A115890 A115891 * A115893 A115894 A115895

Keyword

nonn,base

Author

Giovanni Resta, Feb 06 2006

Extensions

a(19)-a(25) from Donovan Johnson, Sep 30 2011

Status

approved