OFFSET
1,1
REFERENCES
J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 34, pp 13, Ellipses, Paris 2008.
EXAMPLE
sigma(34) = sigma(34+19) = 54.
MATHEMATICA
Select[Range[10^6], DivisorSigma[1, #] == DivisorSigma[1, # + 19] &] (* Vincenzo Librandi, Nov 13 2018 *)
PROG
(PARI) isok(n) = sigma(n+19) == sigma(n); \\ Michel Marcus, Nov 13 2018
(Magma) [n: n in [1..2*10^6] | SumOfDivisors(n) eq SumOfDivisors(n + 19)]; // Vincenzo Librandi, Nov 13 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Jud McCranie, Nov 12 2018
STATUS
approved