%I #32 Nov 20 2018 22:00:25
%S 4,4096,4194304,4294967296,4398046511104,4503599627370496,
%T 4611686018427387904,4722366482869645213696,4835703278458516698824704,
%U 4951760157141521099596496896,401734511064747568885490523085290650630550748445698208825344
%N Powers of 4 with initial digit 4.
%C Appearances to the contrary, this sequence is not recursive with a geometric progression factor of 1024. Examples of a(n+1)/a(n) which are not 1024 are a(10)/a(9) = a(20)/a(19) = a(30)/a(29) = a(57)/a(56) = a(67)/a(66) = 2^106 or a(39)/a(38) = a(48)/a(47)= a(86)/a(85) = 2^116. - _R. J. Mathar_, Jan 10 2008
%C Therefore this sequence differs from A013830. - _Georg Fischer_, Oct 06 2018
%H Muniru A Asiru, <a href="/A067482/b067482.txt">Table of n, a(n) for n = 1..71</a>
%H Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/NonRecursions.html">Non Recursions</a>
%F a(n) = 4^A242594(n).
%t DeleteCases[Table[If[StringStartsQ[ToString[4^n],"4"],4^n], {n, 100}], Null] (* _Stefano Spezia_, Oct 06 2018 *)
%o (GAP) Filtered(List([0..100],n->4^n),i->ListOfDigits(i)[1]=4); # _Muniru A Asiru_, Oct 06 2018
%Y Cf. A000302, A067483, A013830, A242594.
%K base,easy,nonn
%O 1,1
%A _Amarnath Murthy_, Feb 09 2002