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- #!/usr/bin/ruby
- # Largest prime factor of numerator of Sum_{k=0...n} 1/k!, with a(0) = 1.
- # https://oeis.org/A102469
- include('../../../factordb/auto.sf')
- func a(n) is cached {
- sum(0..n, {|k|
- 1/k!
- }).nu
- }
- #~ for n in (46 .. 1000) {
- #~ var k = a(n)
- #~ #say "#{k} = #{k.factor{.ecm_factor(50_000, 10)}.first(-1).join(' * ')}"
- #~ say "#{k} = #{k.factor.first(-1).join(' * ')}"
- #~ }
- #~ __END__
- var fh = File('bfile.txt').open_w
- fh.autoflush(true)
- for n in (0..10000) {
- #next if (n < 72)
- 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(numerator(sum(k=0, n, 1/k!)))[,1]); \\ ~~~~
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