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

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..15.

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: A011205 A167133 A144567 * A010718 A247872 A306400

Adjacent sequences: A215729 A215730 A215731 * A215733 A215734 A215735

Keyword

nonn,base,hard,more

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

Status

approved