A095990 Numbers with ordered prime signature (1,2).

18, 50, 75, 98, 147, 242, 245, 338, 363, 507, 578, 605, 722, 845, 847, 867, 1058, 1083, 1183, 1445, 1587, 1682, 1805, 1859, 1922, 2023, 2523, 2527, 2645, 2738, 2883, 3179, 3362, 3698, 3703, 3757, 3971, 4107, 4205, 4418, 4693, 4805, 5043, 5547, 5618, 5819

Offset: 1

Author

Alford Arnold, Jul 18 2004

Keywords

• easy
• nonn

Comments

Numbers of the form p*q^2 where p and q are primes with p < q.

A054753 contains natural numbers with ordered prime signatures (2,1) and (1,2).

Examples

			18 = 2*3*3, 50 = 2*5*5, 75 = 3*5*5, 98 = 2*7*7, 147 = 3*7*7, ...
		

Links

• Enrique Pérez Herrero, Table of n, a(n) for n = 1..3000
• OEIS Wiki, Ordered prime signatures

Crossrefs

Subsequence of A071365.

Cf. A054753, A095904, A096156.

Programs

Mathematica

Take[ Sort[ Flatten[ Table[ Prime[p]*Prime[q]^2, {q, 2, 16}, {p, q - 1}]]], 46] (* Robert G. Wilson v, Jul 23 2004 *)

PARI

list(lim)=my(v=List());forprime(q=3, sqrtint(lim\2), forprime(p=2, min(lim\q^2,q-1), listput(v,p*q^2))); Set(v) \\ Charles R Greathouse IV, Feb 26 2014

Extensions

Edited and extended by Robert G. Wilson v, Jul 23 2004