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- #!/usr/bin/ruby
- # Numbers k such that Omega(k) = Omega(2^k-1), where Omega(k) is the number of prime factors of k counted with multiplicity (A001222).
- # https://oeis.org/A155900
- # Known terms:
- # 1, 2, 3, 4, 5, 7, 8, 9, 13, 16, 17, 19, 27, 31, 32, 49, 61, 89, 107, 127, 521, 607
- # New terms:
- # 1279, 2203, 2281, 3217
- # added using factordb.com by ~~~~
- include("../../../factordb/auto.sf")
- func isok(k) {
- var t = (2**k - 1)
- var r = k.bigomega
- say "[#{r},#{k}] Checking: #{t}"
- if (try { bigomega(t) == r } catch { t.is_almost_prime(r) }) {
- return true
- }
- return false
- }
- for n in (3226.inc .. 1e5) {
- if (isok(n)) {
- #print(n, ", ")
- die "New term: #{n}\n"
- }
- }
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