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A077378
Squarefree numbers whose external as well as internal digits form a squarefree number.
4
123, 127, 129, 130, 131, 133, 134, 137, 139, 151, 154, 155, 157, 159, 161, 163, 165, 167, 170, 173, 174, 177, 179, 221, 222, 223, 226, 229, 231, 233, 239, 251, 253, 259, 262, 263, 266, 269, 271, 273, 321, 323, 327, 329, 330, 331, 334, 335, 337, 339, 353, 354, 355, 357, 358
OFFSET
1,1
COMMENTS
Here 1 is treated as not squarefree. - Andrew Howroyd, Sep 19 2024
PROG
(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
CROSSREFS
Intersection of A077376 and A077377.
Sequence in context: A308004 A192231 A341992 * A031509 A351479 A247616
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Nov 06 2002
EXTENSIONS
Offset changed and a(29) onwards from Andrew Howroyd, Sep 19 2024
STATUS
approved