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
Keywords
Examples
Number 28 (with sigma(28) = 56) is in sequence because sigma(26+sigma(26)) = sigma(84) = 224 = 4*56.
Programs
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Magma
[n:n in[1..10000] | SumOfDivisors(n+SumOfDivisors(n)) eq 4*SumOfDivisors(n)]
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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
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PARI
for(n=1,10^4,if(sigma(n+sigma(n))==4*sigma(n),print1(n,", "))) \\ Derek Orr, Sep 07 2014