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A333402 Numbers m such that the largest digit in the decimal expansion of 1/m is 1. 13
1, 9, 10, 90, 99, 100, 900, 909, 990, 999, 1000, 9000, 9009, 9090, 9900, 9990, 9999, 10000, 90000, 90009, 90090, 90900, 90909, 99000, 99900, 99990, 99999, 100000, 900000, 900009, 900090, 900900, 909000, 909090, 990000, 990099, 999000, 999900, 999990, 999999, 1000000 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
If m is a term, 10*m is also a term.
If m is a term then m has only digits {1}, {9}, {1,0} or {9,0} in its decimal representation, but this is not sufficient to be a term (see examples).
Some subsequences below (not exhaustive, see crossrefs):
m = 10^k, k >= 0, hence m is in A011557 = {1, 10, 100, 1000, 10000, ...};
m = 9*10^k, k >= 0, hence m is in A052268 = {9, 90, 900, 9000, 90000, ...};
m = 10^k-1, k >= 1, hence m is in A002283 = {9, 99, 999, 9999, 99999, ...};
m = 9*(10^k+1), k >= 1, hence m is in 9*A000533 = {99, 909, 9009, 90009, ...};
m = 9+100*(100^k-1)/11, k >= 0, hence m is in 9*A094028 = {9, 909, 90909, 9090909, ...}.
LINKS
FORMULA
A333236(a(n))= 1.
EXAMPLE
As 1/101 = 0.009900990099..., 101 is not a term.
As 1/909 = 0.001100110011..., 909 is a term.
As 1/9099 = 0.000109902187..., 9099 is not a term.
As 1/9999 = 0.000100010001..., 9999 is also a term.
MATHEMATICA
Select[Range[10^4], Max @ RealDigits[1/#][[1]] == 1 &] (* Amiram Eldar, Mar 19 2020 *)
PROG
(Python)
from itertools import count, islice
def A333402_gen(startvalue=1): # generator of terms >= startvalue
for m in count(max(startvalue, 1)):
k = 1
while k <= m:
k *= 10
rset = {0}
while True:
k, r = divmod(k, m)
if max(str(k)) > '1':
break
else:
if r in rset:
yield m
break
rset.add(r)
k = r
while k <= m:
k *= 10
A333402_list = list(islice(A333402_gen(), 30)) # Chai Wah Wu, Feb 17 2022
CROSSREFS
Cf. A333236, A333237 (similar, with 9).
Subsequences: A002283, A011557, A052268.
Subsequences: 9*A000533, 9*A094028, 9*A135577, 9*A261544, 9*A330135.
Sequence in context: A136880 A136874 A136881 * A360947 A248306 A336690
KEYWORD
nonn,base
AUTHOR
Bernard Schott, Mar 19 2020
EXTENSIONS
More terms from Jinyuan Wang, Mar 19 2020
STATUS
approved

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Last modified May 18 03:36 EDT 2024. Contains 372618 sequences. (Running on oeis4.)