A086560 Start of first run of n successive numbers in which i-th number has exactly i distinct prime divisors for i = 1..n.

2, 5, 64, 1867, 491851, 17681491, 35565206671, 43194825904693

Offset: 1

Author

Amarnath Murthy, Aug 30 2003

Keywords

• nonn
• hard
• more

Examples

			a(3) = 64, as 64 has 1, 65 has 2 and 66 has 3 prime divisors: 64 = 2^6, 65 = 5*13 and 66 = 2*3*11.
		

References

• J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 64, p. 23, Ellipses, Paris 2008.

Crossrefs

Cf. A001221, A072875.

Extensions

More terms from Don Reble, Sep 13 2003

a(7) from Donovan Johnson, Mar 06 2008

a(8) from Donovan Johnson, Jul 19 2011