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A171701
The first n-fold (at least) intrinsically 2-palindromic number (in base ten)
24
3, 8, 18, 24, 48, 60, 120, 120, 180, 336, 360, 360, 720, 720, 720, 840, 1260, 1440, 1680, 1680, 2520, 2520, 2520, 2520, 5040, 5040, 5040, 5040, 5040, 5040, 7560, 7560, 10080, 10080, 10080, 10080, 15120, 15120, 15120, 15120, 30160, 20160, 25200, 25200
OFFSET
1,1
FORMULA
If d'(k) is the number of divisors of k minus 1 for square k and minus 2 for numbers of the form m^2+m, then a(n) is the first k for which d'(k)/2>n-1.
KEYWORD
nonn,base
AUTHOR
James G. Merickel, Dec 16 2009
STATUS
approved