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 A077378 #17 Feb 19 2025 10:26:04
%S A077378 123,127,129,130,131,133,134,137,139,151,154,155,157,159,161,163,165,
%T A077378 167,170,173,174,177,179,221,222,223,226,229,231,233,239,251,253,259,
%U A077378 262,263,266,269,271,273,321,323,327,329,330,331,334,335,337,339,353,354,355,357,358
%N A077378 Squarefree numbers whose external as well as internal digits form a squarefree number.
%C A077378 Here 1 is treated as not squarefree. - _Andrew Howroyd_, Sep 19 2024
%H A077378 Paolo Xausa, <a href="/A077378/b077378.txt">Table of n, a(n) for n = 1..10000</a>
%t A077378 A077378Q[k_] := k >= 100 && SquareFreeQ[k] && SquareFreeQ[FromDigits[#[[{1, -1}]]]] && FromDigits[#[[2;; -2]]] > 1 && SquareFreeQ[FromDigits[#[[2;; -2]]]] & [IntegerDigits[k]];
%t A077378 Select[Range[500], A077378Q] (* _Paolo Xausa_, Feb 19 2025 *)
%o A077378 (PARI) isok(k)={if(issquarefree(k) && k>=100, my(b=10^logint(k,10), m=k%b\10); m!=1 && issquarefree(m) && issquarefree(k\b*10+k%10), 0)} \\ _Andrew Howroyd_, Sep 19 2024
%Y A077378 Intersection of A077376 and A077377.
%Y A077378 Cf. A005117, A077379, A077380.
%K A077378 base,easy,nonn
%O A077378 1,1
%A A077378 _Amarnath Murthy_, Nov 06 2002
%E A077378 Offset changed and a(29) onwards from _Andrew Howroyd_, Sep 19 2024