A031147 - OEIS

%I #20 Sep 10 2024 12:40:59

%S 1,1024,4398046511104,8796093022208,604462909807314587353088,

%T 309485009821345068724781056,1267650600228229401496703205376,

%U 5070602400912917605986812821504,784637716923335095479473677900958302012794430558004314112

%N Smallest power of 2 containing exactly n zeros.

%F a(n) = 2^A031146(n). - _M. F. Hasler_, Jun 15 2018 (corrected by _Sean A. Irvine_, Apr 11 2020)

%t Table[SelectFirst[{#,DigitCount[#,10,0]}&/@(2^Range[0,2000]),#[[2]]==n&],{n,0,8}][[;;,1]] (* _Harvey P. Dale_, Sep 10 2024 *)

%o (PARI) A031147(n)=for(k=n, oo, #select(d->!d, digits(2^k))==n&&return(2^k)) \\ _M. F. Hasler_, Jun 15 2018

%Y Cf. A031146.

%K nonn,easy,base

%O 0,2

%A _N. J. A. Sloane_

%E More terms from _Erich Friedman_

%E a(8) added by _M. F. Hasler_, Jun 16 2018