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A375728
Least number k such that the concatenation of n consecutive numbers from k to k+n-1 is divisible by their sum.
0
1, 1, 2, 3, 1, 5, 186, 13, 4, 6, 10, 5, 60, 7, 6, 249, 200, 158, 810, 1051, 12, 21, 4972, 325, 326, 100, 20, 27, 948, 32776, 7212, 7105, 17, 23, 27256, 5, 99, 880933, 14, 42121, 12, 146, 460, 77, 11, 14205, 17171694, 220697, 753, 29926, 200, 129, 235405, 13, 1206
OFFSET
1,3
EXAMPLE
a(7) = 186 because 186 is the least number such that
(186||187||188||189||190||191||192)/(186+187+188+189+190+191+192) = 186187188189190191192/1323 = 140731056832343304 that is an integer.
PROG
(Python)
from itertools import count
def a(n):
s, strs = sum(range(1, n+1)), list(map(str, range(1, n+1)))
for k in count(1):
if int("".join(strs))%s == 0: return k
s, strs = s + n, strs[1:] + [str(k+n)]
print([a(n) for n in range(1, 47)]) # Michael S. Branicky, Aug 25 2024
CROSSREFS
Cf. A173712.
Sequence in context: A137211 A212275 A189036 * A319952 A174665 A256470
KEYWORD
nonn,base
AUTHOR
Paolo P. Lava, Aug 25 2024
STATUS
approved