OFFSET
0,2
COMMENTS
a(123) > 10^11. - Giovanni Resta, Sep 15 2017
LINKS
EXAMPLE
Divisors of 1183 are 1, 7, 13, 91, 169 and 1183: sigma(1) + sigma(7) + sigma(13) + sigma(91) + sigma(169) + sigma(1183)= 1 + 8 + 14 + 112 + 183 + 1464 = 1782 = sigma(1183+3) and 1183 is the least number to have this property.
MAPLE
with(numtheory): P:=proc(q) local a, b, j, k, n; for n from 0 to q do for k from 1 to q do
a:=divisors(k); b:=add(sigma(a[j]), j=1..nops(a));
if sigma(k+n)=b then print(k); break; fi; od; od; end: P(10^6);
PROG
(PARI) a(n) = my(k = 1); while(sigma(k+n) != sumdiv(k, d, sigma(d)), k++); k; \\ Michel Marcus, Sep 19 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Sep 05 2017
EXTENSIONS
a(15), a(29), a(39), a(75), a(84), a(89), a(111) from Giovanni Resta, Sep 15 2017
STATUS
approved