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A029471 Numbers k that divide the (left) concatenation of all numbers <= k written in base 2 (most significant digit on left). 141
1, 85, 145, 245, 1189, 356717, 19590671, 35741759, 791822369, 25313027035 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
No other terms below 3*10^10.
LINKS
MATHEMATICA
b = 2; c = {}; Select[Range[10^4], Divisible[FromDigits[c = Join[IntegerDigits[#, b], c], b], #] &] (* Robert Price, Mar 12 2020 *)
PROG
(Python)
from itertools import count
def a029471():
total = 0
power_of_two = 1
index_of_two = 0
length_of_string = 0
for n in count(1):
total += (n<<length_of_string)
if n == power_of_two:
power_of_two *= 2
index_of_two += 1
length_of_string += index_of_two
if total % n == 0:
yield n
# Christian Perfect, Feb 07 2014
(Python)
def concat_mod(base, k, mod): ... # See A029479
for k in range(1, 3*10**10):
if concat_mod(2, k, k) == 0: print(k) # Jason Yuen, Mar 24 2024
CROSSREFS
Cf. A007088.
Sequence in context: A259219 A273123 A239527 * A083750 A043684 A043574
KEYWORD
nonn,base,hard,more
AUTHOR
EXTENSIONS
One more term from Larry Reeves (larryr(AT)acm.org), Dec 03 2001
Edited and updated by Larry Reeves (larryr(AT)acm.org), Apr 12 2002
a(7)-a(8) from Max Alekseyev, May 12 2011
a(9)-a(10) from Jason Yuen, Mar 24 2024
STATUS
approved

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Last modified May 29 11:49 EDT 2024. Contains 372940 sequences. (Running on oeis4.)