OFFSET
1,4
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
EXAMPLE
a(10) = sigma(10) - (2 + 5) = 1 + 2 + 5 + 10 - 7 = 11.
MATHEMATICA
sigma1 = Table[Plus @@ Divisors[n], {n, 100}]; sopfr = Prepend[ Array[ Plus @@ Map[ Times @@ #1 &, FactorInteger[ # ] ] &, 100, 2 ], 0 ]; Table[sigma1[[n]] - sopfr[[n]], {n, 100}] (* Alonso del Arte, Dec 01 2004 *)
PROG
(PARI) sodf(n)=local(x); x=factor(n); sum(i=1, length(x[, 1]), sum(j=1, x[i, 2], x[i, 1])); for(i=1, 60, print1(sigma(i)-sodf(i)", "))
(PARI)
A001414(n) = ((n=factor(n))[, 1]~*n[, 2]);
CROSSREFS
KEYWORD
nonn
AUTHOR
Jon Perry, Jul 27 2003
EXTENSIONS
Data section extended up to a(82) by Antti Karttunen, Jul 06 2024
STATUS
approved