A179643 - OEIS

A179643

Products of exactly 2 distinct squares of primes and a different prime (p^2 * q^2 * r).

180, 252, 300, 396, 450, 468, 588, 612, 684, 700, 828, 882, 980, 1044, 1100, 1116, 1300, 1332, 1452, 1476, 1548, 1575, 1692, 1700, 1900, 1908, 2028, 2124, 2156, 2178, 2196, 2205, 2300, 2412, 2420, 2450, 2475, 2548, 2556, 2628, 2844, 2900, 2925, 2988

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

A050326(a(n)) = 5, subsequence of A225228. - Reinhard Zumkeller, May 03 2013

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

Will Nicholes, Prime Signatures

Index to sequences related to prime signature

EXAMPLE

180 = 2^2 * 3^2 * 5, 252 = 2^2 * 3^2 * 7, 300 = 2^2 * 3 * 5^2, ...

MATHEMATICA

f[n_]:=Sort[Last/@FactorInteger[n]]=={1, 2, 2}; Select[Range[3000], f]

PROG

(PARI) list(lim)=my(v=List(), t); forprime(p=2, sqrt(lim\12), forprime(q=p+1, sqrt(lim\p^2\2), t=(p*q)^2; forprime(r=2, lim\t, if(p==r||q==r, next); listput(v, t*r)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 19 2011

CROSSREFS

Cf. A006881, A007304, A065036, A085986, A085987, A178739, A179642.

Cf. A179695.

Sequence in context: A309380 A030636 A350372 * A160134 A135193 A095650

Adjacent sequences: A179640 A179641 A179642 * A179644 A179645 A179646

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Jul 21 2010

STATUS

approved