OFFSET
1,2
COMMENTS
Equivalently, numbers whose digits have the coefficient of variation (or relative population standard deviation) equal to 1/2.
Any number obtained without leading zeros from a permutation of the digits of a given term of the sequence is also a term.
The concatenation of several copies of any term is a term. - Robert Israel, Mar 24 2024
LINKS
EXAMPLE
1133 is a term since the mean of the digits is (1 + 1 + 3 + 3)/4 = 2 and the standard deviation of the digits is sqrt(((1-2)^2 + (1-2)^2 + (3-2)^2 + (3-2)^2)/4) = 1.
MATHEMATICA
DigStd[n_]:=If[n==0||IntegerLength[n]==1, 0, Sqrt[(IntegerLength[n]-1)/IntegerLength[n]]StandardDeviation[IntegerDigits[n]]]; Select[Range[0, 12000], Mean[IntegerDigits[#]]==2DigStd[#]&]
PROG
(Python)
from itertools import count, islice
def A371463_gen(startvalue=0): # generator of terms >= startvalue
return filter(lambda n:5*sum(s:=tuple(map(int, str(n))))**2 == len(s)*sum(d**2 for d in s)<<2, count(max(startvalue, 0)))
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Stefano Spezia, Mar 24 2024
STATUS
approved