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 A077377 #15 Feb 19 2025 10:26:08
%S A077377 1,2,3,5,6,7,10,11,13,14,15,17,19,21,22,23,26,29,30,31,33,34,35,37,38,
%T A077377 39,41,42,43,46,47,51,53,55,57,58,59,61,62,65,66,67,69,70,71,73,74,77,
%U A077377 78,79,82,83,85,86,87,89,91,93,94,95,97,101,103,105,107,109,110,111,113
%N A077377 Squarefree numbers whose external digits form a squarefree number.
%H A077377 Charles R Greathouse IV, <a href="/A077377/b077377.txt">Table of n, a(n) for n = 1..10000</a>
%t A077377 A077377Q[k_] := SquareFreeQ[k] && (k < 10 || SquareFreeQ[FromDigits[IntegerDigits[k][[{1, -1}]]]]);
%t A077377 Select[Range[200], A077377Q] (* _Paolo Xausa_, Feb 19 2025 *)
%o A077377 (PARI) list(lim)=my(v=List(),n,t); for(d=0,logint(lim\=1,10), t=10^d; forsquarefree(k=t,min(10*t-1,lim), if(issquarefree(k[1]\t*10 + k[1]%10), listput(v,k[1])))); Vec(v) \\ _Charles R Greathouse IV_, Feb 14 2018
%Y A077377 Cf. A005117, A077376, A077378, A077379, A077380.
%K A077377 base,easy,nonn
%O A077377 1,2
%A A077377 _Amarnath Murthy_, Nov 06 2002
%E A077377 a(1) inserted by _Charles R Greathouse IV_, Feb 14 2018