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Dropping first and last digit of n leaves its largest prime factor.
0

%I #2 Mar 30 2012 17:40:34

%S 128,150,175,250,378,432,450,672,750,875,1024,1197,1537,1593,1675,

%T 2112,2176,2596,3179,3192,3478,3792,3977,4050,4199,4232,4895,5412,

%U 5612,6171,6794,7738,8294,8533,9072,9196,9796,10614,10731,11371,11398

%N Dropping first and last digit of n leaves its largest prime factor.

%e Dropping first and last digit of 4199 leaves 19, which is the largest prime factor of 4199=13*17*19.

%t Select[Range[100, 50000], (First@Last@FactorInteger@# == FromDigits@Rest@Most@IntegerDigits@#) &]

%K base,easy,nonn

%O 1,1

%A _Giovanni Resta_, Feb 15 2006