A246911 Numbers n such that sigma(n+sigma(n)) = 4*sigma(n).

28, 66, 348, 496, 840, 920, 1320, 1416, 1602, 1770, 1896, 1920, 2040, 2280, 2556, 3000, 3360, 3720, 4440, 4920, 5456, 5640, 5826, 7080, 7392, 8010, 8040, 8128, 8298, 10528, 10680, 11424, 12768, 12840, 13080, 15108, 15504, 17880, 18120, 18720, 18840, 20832

Offset

1,1

Links

Table of n, a(n) for n=1..42.

Example

Number 28 (with sigma(28) = 56) is in sequence because sigma(26+sigma(26)) = sigma(84) = 224 = 4*56.

Maple

with(numtheory): A246911:=n->`if`(sigma(n+sigma(n)) = 4*sigma(n), n, NULL): seq(A246911(n), n=1..3*10^4); # Wesley Ivan Hurt, Sep 07 2014

Prog

(Magma) [n:n in[1..10000] | SumOfDivisors(n+SumOfDivisors(n)) eq 4*SumOfDivisors(n)]
(PARI)
for(n=1, 10^4, if(sigma(n+sigma(n))==4*sigma(n), print1(n, ", "))) \\ Derek Orr, Sep 07 2014

Crossrefs

Cf. A000203, A239050, A246456, A246909, A246910, A246912, A246913, A246914.

Sequence in context: A290543 A344044 A183230 * A323918 A039460 A245990

Adjacent sequences: A246908 A246909 A246910 * A246912 A246913 A246914

Keyword

nonn

Author

Jaroslav Krizek, Sep 07 2014

Status

approved