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

Author

Jaroslav Krizek, Sep 07 2014

Keywords

• nonn

Examples

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

Crossrefs

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

Programs

Magma

[n:n in[1..10^7] | SumOfDivisors(n+SumOfDivisors(n))eq 5*SumOfDivisors(n)]

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 *)

PARI

for(n=1,10^7,if(sigma(n+sigma(n))==5*sigma(n),print1(n,", "))) \\ Derek Orr, Sep 07 2014