A246910 Numbers n such that sigma(n+sigma(n)) = 3*sigma(n).

1, 7, 26, 30, 42, 54, 69, 78, 84, 94, 102, 103, 114, 138, 140, 174, 222, 258, 354, 364, 474, 476, 498, 520, 532, 534, 582, 618, 644, 650, 762, 764, 812, 834, 847, 894, 978, 1002, 1036, 1038, 1050, 1182, 1185, 1194, 1204, 1214, 1362, 1372, 1398, 1434, 1487

Offset: 1

Author

Jaroslav Krizek, Sep 07 2014

Keywords

• nonn

Comments

A246914 gives the primes in this sequence.

Examples

			Number 26 (with sigma(26) = 42) is in sequence because sigma(26+sigma(26)) = sigma(68) = 126 = 3*42.
		

Links

• Martin Møller Skarbiniks Pedersen, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000203, A246456, A246909, A246911, A246912, A246913, A246914, A272027.

Programs

Magma

[n:n in[1..10000] | SumOfDivisors(n+SumOfDivisors(n)) eq 3*SumOfDivisors(n)]

Maple

with(numtheory): A246910:=n->`if`(sigma(n+sigma(n)) = 3*sigma(n),n,NULL): seq(A246910(n), n=1..5000); # Wesley Ivan Hurt, Sep 07 2014

PARI

for(n=1,10^4,if(sigma(n+sigma(n))==3*sigma(n),print1(n,", "))) \\ Derek Orr, Sep 07 2014