A215737 - OEIS

%I #35 Oct 04 2024 00:24:49

%S 1,1,8,7,6,0,6,0,9,6,6,2,2,7,6,9

%N a(n) is the first digit to appear n times in succession in a power of 11.

%t n = 1; x = 1; lst = {};

%t For[i = 1, i <= 10000, i++,

%t z = Split[IntegerDigits[x]]; a = Length /@ z; b = Max[a];

%t For[j = n, j <= b, j++,

%t   AppendTo[lst, First[First[Part[z, First[Position[a, b]]]]]]; n++

%t ]; x = 11 x ]; lst  (* _Robert Price_, Mar 16 2019 *)

%o (Python)

%o def A215737(n):

%o     a, s = 1, tuple(str(i)*n for i in range(10))

%o     while True:

%o         a *= 11

%o         t = str(a)

%o         for i, x in enumerate(s):

%o             if x in t:

%o                 return i # _Chai Wah Wu_, Mar 30 2021

%Y Cf. A001020 (powers of 11), A045875, A215731, A215732.

%K nonn,more,base

%O 1,3

%A _V. Raman_, Aug 22 2012

%E a(10)-a(13) added by _V. Raman_, Apr 30 2012, in correspondence with A215731.

%E a(14) from _Giovanni Resta_, Apr 18 2016

%E a(15) from _Bert Dobbelaere_, Feb 15 2019

%E a(16) from _Paul Geneau de Lamarlière_, Oct 03 2024