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Powers of 2 with initial digit 7.
3

%I #16 Sep 08 2022 08:46:23

%S 70368744177664,72057594037927936,73786976294838206464,

%T 75557863725914323419136,77371252455336267181195264,

%U 79228162514264337593543950336,713623846352979940529142984724747568191373312,730750818665451459101842416358141509827966271488

%N Powers of 2 with initial digit 7.

%H Muniru A Asiru, <a href="/A320863/b320863.txt">Table of n, a(n) for n = 1..170</a>

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

%p select(x->"7"=""||x[1],[2^n$n=0..180])[];

%t Select[2^Range[160], First[IntegerDigits[#]] == 7 &] (* _G. C. Greubel_, Oct 27 2018 *)

%o (GAP) Filtered(List([0..180],n->2^n),i->ListOfDigits(i)[1]=7);

%o (PARI) select(x->(digits(x)[1]==7), vector(200, n, 2^n)) \\ _Michel Marcus_, Oct 27 2018

%o (Magma) [2^n: n in [1..160] | Intseq(2^n)[#Intseq(2^n)] eq 7]; // _G. C. Greubel_, Oct 27 2018

%Y Cf. A000079 (powers of 2), A008952 (leading digit of 2^n), A217400 (numbers starting with 7).

%Y Powers of 2 with initial digit k, (k = 1..7): A067488, A067480, A320859, A320860, A320861, A320862, this sequence.

%K base,nonn

%O 1,1

%A _Muniru A Asiru_, Oct 26 2018