A066681 Badly sieved numbers (A066680) which are not primes.

8, 12, 18, 27, 30, 45, 50, 63, 70, 75, 80, 98, 105, 112, 125, 128, 147, 154, 165, 168, 175, 176, 182, 192, 195, 208, 220, 231, 242, 245, 260, 264, 273, 275, 286, 312, 325, 338, 340, 343, 357, 363, 374, 380, 385, 396, 399, 408

Offset: 1

Author

Reinhard Zumkeller, Dec 31 2001

Keywords

• nonn

Examples

			8 is the first nonprime in A066680, as multiples of 2 are marked only up to 4 = 2^2 and all other multiples of unmarked numbers < 8 do not hit 8.
		

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
• Index entries for sequences generated by sieves

Crossrefs

Cf. A010051.

Programs

Haskell

a066681 n = a066681_list !! (n-1)
a066681_list = filter ((== 0) . a010051) a066680_list
-- Reinhard Zumkeller, Feb 17 2012

Formula

A099104(a(n))*A005171(a(n)) = 1. [Reinhard Zumkeller, Nov 12 2009]