This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A320863 #16 Sep 08 2022 08:46:23 %S A320863 70368744177664,72057594037927936,73786976294838206464, %T A320863 75557863725914323419136,77371252455336267181195264, %U A320863 79228162514264337593543950336,713623846352979940529142984724747568191373312,730750818665451459101842416358141509827966271488 %N A320863 Powers of 2 with initial digit 7. %H A320863 Muniru A Asiru, <a href="/A320863/b320863.txt">Table of n, a(n) for n = 1..170</a> %H A320863 <a href="/index/Di#divseq">Index to divisibility sequences</a> %p A320863 select(x->"7"=""||x[1],[2^n$n=0..180])[]; %t A320863 Select[2^Range[160], First[IntegerDigits[#]] == 7 &] (* _G. C. Greubel_, Oct 27 2018 *) %o A320863 (GAP) Filtered(List([0..180],n->2^n),i->ListOfDigits(i)[1]=7); %o A320863 (PARI) select(x->(digits(x)[1]==7), vector(200, n, 2^n)) \\ _Michel Marcus_, Oct 27 2018 %o A320863 (Magma) [2^n: n in [1..160] | Intseq(2^n)[#Intseq(2^n)] eq 7]; // _G. C. Greubel_, Oct 27 2018 %Y A320863 Cf. A000079 (powers of 2), A008952 (leading digit of 2^n), A217400 (numbers starting with 7). %Y A320863 Powers of 2 with initial digit k, (k = 1..7): A067488, A067480, A320859, A320860, A320861, A320862, this sequence. %K A320863 base,nonn %O A320863 1,1 %A A320863 _Muniru A Asiru_, Oct 26 2018