A031219 Write n in base 5 and juxtapose.

1, 2, 3, 4, 1, 0, 1, 1, 1, 2, 1, 3, 1, 4, 2, 0, 2, 1, 2, 2, 2, 3, 2, 4, 3, 0, 3, 1, 3, 2, 3, 3, 3, 4, 4, 0, 4, 1, 4, 2, 4, 3, 4, 4, 1, 0, 0, 1, 0, 1, 1, 0, 2, 1, 0, 3, 1, 0, 4, 1, 1, 0, 1, 1, 1, 1, 1, 2, 1, 1, 3, 1, 1, 4, 1, 2, 0, 1, 2, 1, 1, 2, 2, 1, 2, 3, 1, 2, 4, 1

Offset

1,2

Comments

An irregular table in which the n-th row lists the base-5 digits of n. - Jason Kimberley, Dec 07 2012

The base-5 Champernowne constant: it is normal in base 5. - Jason Kimberley, Dec 07 2012

Links

Table of n, a(n) for n=1..90.

Mathematica

Flatten@ IntegerDigits[ Range@ 40, 5] (* or *)
almostNatural[n_, b_] := Block[{m = 0, d = n, i = 1, l, p}, While[m <= d, l = m; m = (b - 1) i*b^(i - 1) + l; i++]; i--; p = Mod[d - l, i]; q = Floor[(d - l)/i] + b^(i - 1); If[p != 0, IntegerDigits[q, b][[p]], Mod[q - 1, b]]]; Array[ a[#, 5] &, 105] (* Robert G. Wilson v, Jul 01 2014 *)

Prog

(Magma) &cat[Reverse(IntegerToSequence(n, 5)):n in[1..31]]; // Jason Kimberley, Dec 07 2012
(Python)
from itertools import count, chain, islice
from sympy.ntheory.factor_ import digits
def A031219_gen(): return chain.from_iterable(digits(m, 5)[1:] for m in count(1))
A031219_list = list(islice(A031219_gen(), 30)) # Chai Wah Wu, Jan 07 2022
(Python)
from gmpy2 import digits
from oeis_sequences.OEISsequences import bisection, bsearch
def A031219(n):
    def g(x): return x+(m:=len(digits(x, 5)))*(x+1)-(5*(5**(m-1)-1)>>2)
    def f(x): return n+1+bsearch(g, x)
    return int((s:=digits(a:=bisection(f, n+1, n+1)-n, 5))[n-1-a*(k:=len(s))+(5**k-1>>2)]) # Chai Wah Wu, Mar 02 2026

Crossrefs

Tables in which the n-th row lists the base b digits of n: A030190 and A030302 (b=2), A003137 and A054635 (b=3), A030373 (b=4), this sequence (b=5), A030548 (b=6), A030998 (b=7), A031035 and A054634 (b=8), A031076 (b=9), A007376 and A033307 (b=10). - Jason Kimberley, Dec 06 2012

Sequence in context: A256295 A179078 A256305 * A346689 A071498 A255825

Adjacent sequences: A031216 A031217 A031218 * A031220 A031221 A031222

Keyword

nonn,base,cons,easy,tabf

Author

Clark Kimberling

Status

approved