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%I #23 Jul 20 2024 22:01:32
%S 0,2,18,44,192,315,3396,8556,13327,81785,279267,865357,1799674,
%T 1727603,8760851,63416791,106892452
%N Exponent of least power of 2 having exactly n consecutive 4's in its decimal representation.
%H Popular Computing (Calabasas, CA), <a href="/A094776/a094776.jpg">Two Tables</a>, Vol. 1, (No. 9, Dec 1973), page PC9-16.
%e a(3) = 44 because 2^44 (i.e. 17592186044416) is the smallest power of 2 to contain a run of 3 consecutive fours in its decimal form.
%t a = ""; Do[ a = StringJoin[a, "4"]; b = StringJoin[a, "4"]; k = 1; While[ StringPosition[ ToString[2^k], a] == {} || StringPosition[ ToString[2^k], b] != {}, k++ ]; Print[k], {n, 1, 10} ]
%K more,nonn,base,changed
%O 0,2
%A _Shyam Sunder Gupta_, Aug 26 2007
%E 3 more terms from _Sean A. Irvine_, Jul 19 2010
%E a(14) from _Lars Blomberg_, Jan 24 2013
%E a(15) from _Bert Dobbelaere_, Feb 25 2019
%E a(16) from _Paul Geneau de Lamarlière_, Jun 26 2024
%E a(0)=0 prepended by _Paul Geneau de Lamarlière_, Jul 20 2024
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