OFFSET
1,3
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
EXAMPLE
For n = 4, sigma(4) = 7, from numbers 1 - 7 there are four numbers k such that k is not equal to sigma(d) for any divisor d of n: 2, 4, 5, 6; a(4) = 4.
MATHEMATICA
f[n_] := Block[{c = 0, k = 1, lmt = DivisorSigma[1, n] + 1, sd = DivisorSigma[1, #] & /@ Divisors@ n}, While[k < lmt, If[! MemberQ[sd, k], c++]; k++]; c]; Array[f, 67]
PROG
(PARI)
A184395(n) = length(vecsort(apply(d->sigma(d), divisors(n)), , 8));
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Jan 12 2011
EXTENSIONS
More terms from Antti Karttunen, Aug 24 2017
STATUS
approved