OFFSET
1,1
COMMENTS
When p=2^k+15 is prime (cf. A057197), then 2^(k-1)*p is in this sequence. The terms { 17, 38, 92, 248, 752, 2528, 34688, 531968, 2112512, 8419328, 537116672, 2147975168, ...} are of this from, with k in {1, 2, 3, 4, 5, 6, 8, 10, 11, 12, 15, 16, ...} = A057197. - M. F. Hasler, Jul 18 2016
Any term x of this sequence can be combined with any term y of A141547 to satisfy the property (sigma(x)+sigma(y))/(x+y) = 2, which is a necessary (but not sufficient) condition for two numbers to be amicable. - Timothy L. Tiffin, Sep 13 2016
LINKS
Donovan Johnson, Giovanni Resta and Hiroaki Yamanouchi, Table of n, a(n) for n = 1..69 (terms <= 10^18, first 43 terms from Donovan Johnson and a(44)-a(51) from Giovanni Resta)
EXAMPLE
The abundance of 38 = (1+2+19+38)-76 = -16
MATHEMATICA
Select[Range[1, 10^6], DivisorSigma[1, #] - 2 # == - 16 &] (* Vincenzo Librandi, Sep 14 2016 *)
PROG
(PARI) for(n=1, 1000000, if(((sigma(n)-2*n)==-16), print1(n, ", ")))
(Magma) [n: n in [1..9*10^6] | (SumOfDivisors(n)-2*n) eq -16]; // Vincenzo Librandi, Sep 14 2016
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jason G. Wurtzel, Nov 25 2006
EXTENSIONS
a(17) to a(30) from Klaus Brockhaus, Nov 29 2006
STATUS
approved