A077378 - OEIS

%I #10 Sep 19 2024 21:59:21

%S 123,127,129,130,131,133,134,137,139,151,154,155,157,159,161,163,165,

%T 167,170,173,174,177,179,221,222,223,226,229,231,233,239,251,253,259,

%U 262,263,266,269,271,273,321,323,327,329,330,331,334,335,337,339,353,354,355,357,358

%N Squarefree numbers whose external as well as internal digits form a squarefree number.

%C Here 1 is treated as not squarefree. - _Andrew Howroyd_, Sep 19 2024

%o (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 Intersection of A077376 and A077377.

%Y Cf. A077379, A077380.

%K base,easy,nonn,changed

%O 1,1

%A _Amarnath Murthy_, Nov 06 2002

%E Offset changed and a(29) onwards from _Andrew Howroyd_, Sep 19 2024