|
|
A113999
|
|
a(n) = Sum_{ k, k|n } 10^(k-1).
|
|
11
|
|
|
1, 11, 101, 1011, 10001, 100111, 1000001, 10001011, 100000101, 1000010011, 10000000001, 100000101111, 1000000000001, 10000001000011, 100000000010101, 1000000010001011, 10000000000000001, 100000000100100111
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
|
|
LINKS
|
|
|
FORMULA
|
G.f.: Sum_{n>0} x^n/(1-10*x^n).
|
|
MATHEMATICA
|
A113999[n_]:= DivisorSum[n, 10^(#-1) &];
|
|
PROG
|
(PARI) a(n)=if(n<1, 0, sumdiv(n, k, 10^(k-1)));
(Magma)
A113999:= func< n | (&+[10^(d-1): d in Divisors(n)]) >;
(SageMath)
def A113999(n): return sum(10^(k-1) for k in (1..n) if (k).divides(n))
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|