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Powers of 2 with initial digit 3.
7

%I #22 Sep 08 2022 08:46:23

%S 32,32768,33554432,34359738368,35184372088832,36028797018963968,

%T 36893488147419103232,37778931862957161709568,

%U 302231454903657293676544,38685626227668133590597632,309485009821345068724781056,39614081257132168796771975168,316912650057057350374175801344

%N Powers of 2 with initial digit 3.

%H Muniru A Asiru, <a href="/A320859/b320859.txt">Table of n, a(n) for n = 1..410</a>

%H <a href="/index/Di#divseq">Index to divisibility sequences</a>

%F a(n) = 2^A172404(n).

%p select(x->"3"=""||x[1],[2^n$n=0..120])[];

%t Select[2^Range[0, 100], First[IntegerDigits[#]] == 3 &] (* _G. C. Greubel_, Oct 24 2018 *)

%o (GAP) Filtered(List([0..120],n->2^n),i->ListOfDigits(i)[1]=3);

%o (Magma) [2^n: n in [1..100] | Intseq(2^n)[#Intseq(2^n)] eq 3]; // _G. C. Greubel_, Oct 24 2018

%o (PARI) lista(nn) = {for(n=1, nn, x = 2^n; if (digits(x=2^n)[1] == 3, print1(x, ", ")););} \\ _Michel Marcus_, Oct 25 2018

%Y Cf. A000079 (Powers of 2), A008952 (leading digit of 2^n).

%Y Powers of 2 with initial digit k, (k = 1..4): A067488, A067480, this sequence, A320860.

%Y Cf. A172404.

%K base,nonn

%O 1,1

%A _Muniru A Asiru_, Oct 22 2018