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

1,1

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).

Links

Enrique Pérez Herrero, Table of n, a(n) for n = 1..3000

OEIS Wiki, Ordered prime signatures

Example

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

Mathematica

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

Prog

(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

Crossrefs

Subsequence of A071365.

Cf. A054753, A095904, A096156.

Sequence in context: A093617 A089219 A102835 * A102836 A217750 A180292

Adjacent sequences: A095987 A095988 A095989 * A095991 A095992 A095993

Keyword

easy,nonn

Author

Alford Arnold, Jul 18 2004

Extensions

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

Status

approved