A230009 Numbers n such that sigma(n) = reversal(n+9).

1, 611379, 614077809, 61199999379, 611999999379

Offset

1,2

Comments

If p=68*10^m-69 is prime then 9*p is in the sequence.

611379 and 61199999379 are such terms of the sequence.

a(6) > 6.4*10^12. - Giovanni Resta, Dec 13 2013

Links

Table of n, a(n) for n=1..5.

Example

sigma(1)=1=reversal(10)=reversal(1+9),
sigma(611379)=883116=reversal(611388)=reversal(611379+9).

Mathematica

Select[Range[700000], DivisorSigma[1, #] == FromDigits[Reverse[IntegerDigits[#+9]]]&]

Crossrefs

Cf. A000203, A004086, A230021.

Sequence in context: A235069 A233938 A237784 * A156866 A317480 A206510

Adjacent sequences: A230006 A230007 A230008 * A230010 A230011 A230012

Keyword

nonn,base,more

Author

Farideh Firoozbakht, Dec 06 2013

Extensions

a(3)-a(5) from Giovanni Resta, Dec 13 2013

Status

approved