A215732 a(n) is the first digit to appear n times in succession in a power of 2.

1, 5, 7, 5, 6, 8, 7, 1, 9, 9, 6, 3, 2, 9, 1, 4

Offset

1,2

Comments

Assumes that there are no 2 digits that appear n times in succession for the first time in the same power of 2. - Chai Wah Wu, Apr 26 2019

Links

Table of n, a(n) for n=1..16.

Example

2^16 = 65536 is the first power of 2 with a repeated digit (cf. A045875), with 5 repeated, so a(2) = 5. - N. J. A. Sloane, Aug 23 2012

Mathematica

n = 1; x = 1; lst = {};
For[i = 1, i <= 10000, i++,
z = Split[IntegerDigits[x]]; a = Length /@ z; b = Max[a];
For[j = n, j <= b, j++,
  AppendTo[lst, First[First[Part[z, First[Position[a, b]]]]]]; n++
]; x = 2 x ]; lst (* Robert Price, Mar 16 2019 *)

Prog

(Python)
def A215732(n):
    l, x = [str(d)*n for d in range(10)], 1
    for m in range(10**9):
        s = str(x)
        for k in range(10):
            if l[k] in s:
                return k
        x *= 2
    return 'search limit reached'
# Chai Wah Wu, Dec 17 2014

Crossrefs

Cf. A045875, A215733, A215734, A215735.

Sequence in context: A167133 A144567 A372204 * A010718 A247872 A306400

Adjacent sequences: A215729 A215730 A215731 * A215733 A215734 A215735

Keyword

nonn,base,hard,more,changed

Author

V. Raman, Aug 22 2012

Extensions

a(11)-a(13) added by T. D. Noe, Sep 04 2012

a(14) added by T. D. Noe, Sep 06 2012

a(15) from Bert Dobbelaere, Feb 25 2019

a(16) from Paul Geneau de Lamarlière, Jun 26 2024

Status

approved