cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A090315 Least k such that k and digit reversal of k both have n divisors, or 0 if no such number exists.

Original entry on oeis.org

1, 2, 4, 6, 14641, 44, 0, 24, 484, 272, 0, 294, 0, 291008, 44944, 264, 0, 252, 0, 2992, 0, 2532352, 0, 2508, 10004000600040001, 2977792, 1002001, 2112, 0, 63536, 0, 4224, 0, 44356665344, 0, 2772, 0, 2380651036672, 0, 42224, 0, 6336, 0, 2937856, 698896, 0
Offset: 1

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Author

Amarnath Murthy, Dec 01 2003

Keywords

Comments

For a(7) one needs a number of the form p^6 whose digit reversal is q^6, p, q are primes. Hence a(7) perhaps is zero (not sure). Conjecture: There are infinitely many nonzero terms as well as zeros in this sequence.
Zeros are unproved. I have checked for a(21) up to 10^13, a(46) up to 10^14, a(33) up to 10^18, a(39) up to 10^20, a(35) up to 10^30 and the rest (7, 11, 13, 17, 19, 23, 29, 31, 37, 41 and 43) up to at least 10^48. - David Wasserman, Nov 01 2005

Examples

			a(8) =24, tau(24) = tau(42) = 8.

Crossrefs

Cf. A083753.

Extensions

More terms from David Wasserman, Nov 01 2005
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