A059391 a(1)=4; a(n) is the smallest number m > a(n-1) such that Omega(m + a(i)) = Omega(m) - Omega(a(i)) for i = 1..(n-1) where Omega(k) is the number of prime divisors of k counted with multiplicity.

4, 27, 208, 18630, 780856896

Offset

1,1

Comments

Conjecture: Omega(a(n)) = n-th prime.

The conjecture is false because Omega(780856896) = 10. - Sean A. Irvine, Sep 19 2022

Next term > 10000000000. - Sean A. Irvine, Sep 20 2022

Links

Table of n, a(n) for n=1..5.

Crossrefs

Cf. A001222, A059333, A059363.

Sequence in context: A193221 A091121 A026005 * A371786 A190738 A361717

Adjacent sequences: A059388 A059389 A059390 * A059392 A059393 A059394

Keyword

nonn,hard,more

Author

Naohiro Nomoto, Jan 29 2001

Extensions

Name simplified and a(5) from Sean A. Irvine, Sep 19 2022

Status

approved