OFFSET
1,2
LINKS
Altug Alkan, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = A069789(n) - n. - Michel Marcus, Feb 10 2017
EXAMPLE
a(4) = 8 because sigma(4) = 7 divides sigma(4 + 8) = 28 and 8 is the least positive number with this property.
MATHEMATICA
Table[k = 1; While[! Divisible[DivisorSigma[1, n + k], DivisorSigma[1, n]], k++]; k, {n, 120}] (* Michael De Vlieger, Feb 10 2017 *)
PROG
(PARI) a(n) = my(k = 1); while (sigma(n+k) % sigma(n) != 0, k++); k;
CROSSREFS
KEYWORD
nonn
AUTHOR
Altug Alkan, Feb 10 2017
STATUS
approved