A215736 - OEIS

%I #30 Jul 20 2024 08:12:35

%S 1,1,7,9,5,7,3,1,0,0,3,4,6,5,9,1

%N a(n) is the first digit to appear n times in succession in a power of 7.

%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 = 7 x ]; lst (* _Robert Price_, Mar 16 2019 *)

%Y Cf. A215730, A045875, A215732.

%K nonn,base,hard,more

%O 1,3

%A _V. Raman_, Aug 22 2012

%E a(10) added by _V. Raman_, Nov 23 2013

%E a(11)-a(13) from _Giovanni Resta_, Apr 19 2016

%E a(14)-a(15) from _Bert Dobbelaere_, Feb 15 2019

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