A138207 a(n) is the first term in a chain of at least n consecutive numbers each with exactly 7 distinct prime factors.

510510, 965009045, 30989984674, 1673602584618, 66298619667606

Offset: 1

Author

Donovan Johnson, Mar 06 2008

Keywords

• nonn
• more

Comments

a(5) > 10^13.

a(6) > 2 * 10^15. - Toshitaka Suzuki, Jun 23 2025

Links

• Roger B. Eggleton and James A. MacDougall, Consecutive integers with equally many principal divisors, Math. Mag. 81 (2008), 235-248. [_T. D. Noe_, Oct 13 2008]

Crossrefs

Cf. A087977, A087978, A138206, A154573.

Extensions

a(4) from Donovan Johnson, Jan 15 2009

a(5) from Toshitaka Suzuki, Apr 06 2025