A171701 The first n-fold (at least) intrinsically 2-palindromic number (in base ten)

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

Links

Table of n, a(n) for n=1..44.

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.

Crossrefs

Cf. A171702, A171703, A171704, A171705, A171706, A171740, A171741, A171742.

Sequence in context: A319764 A063597 A328054 * A288249 A360139 A004210

Adjacent sequences: A171698 A171699 A171700 * A171702 A171703 A171704

Keyword

nonn,base

Author

James G. Merickel, Dec 16 2009

Status

approved