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

Author

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

Keywords

• nonn

Links

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

Crossrefs

Cf. A000040.

A033476.

Programs

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 *)

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

Extensions

Additional terms from Jud McCranie, Oct 07 2000