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- #!/usr/bin/ruby
- # Largest prime factor of n^n - n^(n-1) - n^(n-2) - ... - n^2 - n - 1.
- # https://oeis.org/A191624
- include('../../../factordb/auto.sf')
- func a(n) is cached {
- var t = n**n
- for k in (0 .. n-1) {
- t -= n**k
- }
- return t
- }
- #~ for n in (54 .. 1000) {
- #~ var k = a(n)
- #~ #say "#{k} = #{k.factor{.ecm_factor(50_000, 10)}.first(-1).join(' * ')}"
- #~ say "#{k} = #{k.factor{.pm1_factor(1e6)}.first(-1).join(' * ')}"
- #~ }
- #~ __END__
- var fh = File('bfile.txt').open_w
- fh.autoflush(true)
- for n in (3..10000) {
- var row = "#{n} #{gpf(a(n)) || 1}"
- say row
- fh.say(row)
- }
- __END__
- # PARI/GP program:
- a(n) = if(n==0, return(1)); vecmax(factor(n^n - (n^n-1)/(n-1))[,1]); \\ ~~~~
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