[seqfan] Re: Most efficient way to construct a list of pandigital palindromic numbers?

Hans Havermann pxp at rogers.com
Tue Dec 8 05:12:49 CET 2009

Douglas McNeil:

> Does Mma have an idiom for permutations equivalent to python iterators
> which step through a loop without constructing it?

I don't know Python but I was looking at sequential-permutation  
operators in Mathematica earlier and there are "Combinatorica" add-on  
functions such as NextPermutation[p] which gives the permutation  
following p in lexicographic order, and UnrankPermutation[n,l] (it was  
NthPermutation[n,l] in older versions of Mathematica) which gives the  
n-th permutation in the lexicographic list of permutations of list l.

> (For the record, I find 78695 19-digit numbers.)

Quick, how many 20-digit numbers? ;)

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