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

1,1

References

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

Links

Table of n, a(n) for n=1..8.

Example

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.

Crossrefs

Cf. A001221, A072875.

Sequence in context: A076630 A270389 A350956 * A305292 A268211 A246280

Adjacent sequences: A086557 A086558 A086559 * A086561 A086562 A086563

Keyword

nonn,hard,more

Author

Amarnath Murthy, Aug 30 2003

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

Status

approved