A056808 Members of A055932 which are not least prime signatures (cf. A025487).

18, 54, 90, 108, 150, 162, 270, 300, 324, 450, 486, 540, 600, 630, 648, 750, 810, 972, 1050, 1200, 1350, 1458, 1470, 1500, 1620, 1890, 1944, 2100, 2250, 2400, 2430, 2700, 2916, 2940, 3000, 3150, 3240, 3750, 3780, 3888, 4050, 4200, 4374, 4410, 4500, 4800

Offset: 1

Author

Alford Arnold, Aug 22 2000

Keywords

• easy
• nonn

Examples

			18 = 2*3*3 and all prime divisors are consecutive primes but the least prime signature is 12 = 2*2*3; so a(1) = 18.
		

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A025487, A055932, A057335, A161360, A335485, A345974.

Programs

Mathematica

With[{nn = 4800}, Select[Range[2, nn], And[#1 != Times @@ MapIndexed[Prime[First@ #2]^#1 &, Sort[#3, Greater]], Last[#2] == Prime@ Length[#2]] & @@ Apply[Join, {{#1}, Transpose@ #2}] & @@ {#, FactorInteger[#]} &] ] (* Michael De Vlieger, Feb 06 2020 *)

Formula

{a(n) : n >= 1} = {A057335(A335485(k)) : k >= 1}. - Peter Munn, Feb 02 2024

Sum_{n>=1} 1/a(n) = A345974 - A161360 = 0.15229524564163275059... . - Amiram Eldar, Jun 26 2025

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), Nov 28 2000