

A224488


Numbers m such that k*m = Sum_{jm, j < m} sigma(j), where k >= 1 is an integer.


2



4, 10, 42, 90, 2448, 4680, 27144, 117000, 154498509, 222970077, 11049088050, 63554826816
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OFFSET

1,1


COMMENTS

a(13) > 10^11.


LINKS

Table of n, a(n) for n=1..12.


EXAMPLE

The divisors of 10 smaller than 10 are 1, 2 and 5. Since sigma(1) + sigma(2) + sigma(5) = 10, 10 is in the sequence.


MATHEMATICA

Select[Range[2, 120000], Mod[Total@DivisorSigma[1, Most@Divisors@#], #] == 0 &]


CROSSREFS

Cf. A221219.
Sequence in context: A222367 A220817 A114918 * A149213 A149214 A149215
Adjacent sequences: A224485 A224486 A224487 * A224489 A224490 A224491


KEYWORD

nonn,more


AUTHOR

Giovanni Resta, Apr 08 2013


EXTENSIONS

a(9)a(12) and bound on a(13) from Donovan Johnson.


STATUS

approved



