A057602 a(1)=2, a(n+1) is the smallest integer > a(n) such that the smallest prime factor of a(n+1) is the largest prime factor of a(n).

2, 4, 6, 9, 15, 25, 35, 49, 77, 121, 143, 169, 221, 289, 323, 361, 437, 529, 667, 841, 899, 961, 1147, 1369, 1517, 1681, 1763, 1849, 2021, 2209, 2491, 2809, 3127, 3481, 3599, 3721, 4087, 4489, 4757, 5041, 5183, 5329, 5767, 6241, 6557, 6889, 7387, 7921

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

Even numbered terms are squares of successive primes. Odd numbered terms are the product of two successive primes and are the square root of the product of the previous term and the next term - Jud McCranie, Oct 07 2000

Mathematica

Module[{nn=30, pr, ev, od}, pr=Prime[Range[nn]]; ev=pr^2; od=Times @@@ Partition[ pr, 2, 1]; Join[{2}, Riffle[ev, od]]] (* Harvey P. Dale, Mar 02 2015 *)

Crossrefs

Cf. A000040.

A033476.

Sequence in context: A266648 A076922 A157679 * A171646 A074677 A006498

Adjacent sequences: A057599 A057600 A057601 * A057603 A057604 A057605

Keyword

nonn

Author

G. L. Honaker, Jr., Oct 07 2000

Extensions

Additional terms from Jud McCranie, Oct 07 2000

Status

approved