OFFSET
1,1
COMMENTS
Conjecture: sequence is not equal to the sequence of denominators presented in A172495 and A172506. - Jaroslav Krizek, Feb 05 2010
The conjecture is false for both other sequences; see A172495 and A172506 for proofs. - Michael S. Branicky, Nov 30 2022
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..369
FORMULA
a(n) = denominator(Sum_{k=1..n} k/10^A058183(k)). - Stefano Spezia, Nov 30 2022
EXAMPLE
a(1) = 10 as 10*0.1 = 1, a(2) = 25 as 25*0.12 = 3.
PROG
(PARI) a(n) = {my(s = ""); for (k=1, n, s = concat(s, Str(k))); denominator(eval(s)/10^(#s)); } \\ Michel Marcus, Jan 15 2019
(Python)
from itertools import count, islice
def agen(): # generator of terms
num, den, pow = 0, 1, 0
for n in count(1):
sn = str(n)
num = num*10**len(sn) + n
den *= 10**len(sn)
pow += len(sn)
nr, dr, c2, c5 = num, den, pow, pow
while nr%2 == 0 and c2 > 0: nr //= 2; dr //= 2; c2 -= 1
while nr%5 == 0 and c5 > 0: nr //= 5; dr //= 5; c5 -= 1
yield dr
print(list(islice(agen(), 19))) # Michael S. Branicky, Nov 30 2022
CROSSREFS
KEYWORD
base,nonn,frac
AUTHOR
Amarnath Murthy, Nov 24 2002
EXTENSIONS
More terms from Sascha Kurz, Jan 04 2003
More terms from Michel Marcus, Jan 15 2019
STATUS
approved