A246912 Numbers n such that sigma(n+sigma(n)) = 5*sigma(n).

15456, 16920, 48576, 59520, 107160, 153360, 232596, 281916, 306720, 332280, 332640, 358560, 360360, 373104, 383400, 514080, 548772, 556920, 788256, 876960, 884520, 930384, 943344, 950040, 955296, 1234464, 1357020, 1396440, 1421280, 1534080, 1539720, 1582866

Offset

1,1

Links

Table of n, a(n) for n=1..32.

Example

Number 15456 (with sigma(15456) = 48384) is in sequence because sigma(15456+sigma(15456)) = sigma(63840) = 241920 = 5*48384.

Maple

with(numtheory): A246912:=n->`if`(sigma(n+sigma(n)) = 5*sigma(n), n, NULL): seq(A246912(n), n=1..10^6); # Wesley Ivan Hurt, Sep 07 2014

Mathematica

Select[Range[16*10^5], DivisorSigma[1, #+DivisorSigma[1, #]] == 5*DivisorSigma[ 1, #]&] (* Harvey P. Dale, Mar 13 2016 *)

Prog

(Magma) [n:n in[1..10^7] | SumOfDivisors(n+SumOfDivisors(n))eq 5*SumOfDivisors(n)]
(PARI)
for(n=1, 10^7, if(sigma(n+sigma(n))==5*sigma(n), print1(n, ", "))) \\ Derek Orr, Sep 07 2014

Crossrefs

Cf. A000203, A246456, A246909, A246910, A246911, A246913, A246914, A274535 (5*sigma(n)).

Sequence in context: A054840 A210058 A154091 * A035920 A342310 A201344

Adjacent sequences: A246909 A246910 A246911 * A246913 A246914 A246915

Keyword

nonn

Author

Jaroslav Krizek, Sep 07 2014

Status

approved