OFFSET
1,1
COMMENTS
Multiples of 10 are excluded otherwise the sequence would be equal to A011557, for n>0.
a(6) = 11415525 is the first case where the digits of a(n) are more than n+1.
A011557(n) < a(n) <= 15*A094028(n-2) that is 10^n < a(n) <= 5*(100^(n-1)-1)/33, for n>2. - Giovanni Resta, Jul 04 2019
Here a(8) = a(9) and a(10) = a(11). If we would ask for "exactly" n different multiples then a(8) = 2032520325 and a(10) = 103896103896. - Giovanni Resta, Jul 04 2019
EXAMPLE
a(1) = 11 because 1111/11 = 101;
a(2) = 108 because 110808/108 = 1026 and 101088/108 = 936;
a(5) = 102564 because 110256402564/102564 = 1075001, 101025642564/102564 = 985001, 102102564564/102564 = 995501, 102510256464/102564 = 999476, 102561025644/102564 = 999971.
MAPLE
P:=proc(q) local a, b, i, j, n, t: for j from 1 to q do
for n from 10^j+1 to q do if n mod 10>0 then b:=length(n):
t:={}: for i from 1 to b-1 do
a:=((trunc(n/10^i)*10^b+n)*10^i+(n mod 10^i))/n:
if frac(a)=0 then t:=t union {a}: fi: od:
if nops(t)>=j then print(n); break: fi: fi: od: od: end: P(10^9);
CROSSREFS
KEYWORD
base,nonn,more
AUTHOR
Paolo P. Lava, Jul 03 2019
EXTENSIONS
a(9)-a(16) from Giovanni Resta, Jul 04 2019
STATUS
approved