A179642 Product of exactly 5 primes, 3 of which are distinct.

120, 168, 180, 252, 264, 270, 280, 300, 312, 378, 396, 408, 440, 450, 456, 468, 520, 552, 588, 594, 612, 616, 680, 684, 696, 700, 702, 728, 744, 750, 760, 828, 882, 888, 918, 920, 945, 952, 980, 984, 1026, 1032, 1044, 1064, 1100, 1116, 1128, 1144, 1160

Offset

1,1

Links

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

Will Nicholes, Prime Signatures

Example

120=2^3*3*5, 168=2^3*3*7, 180=2^2*3^2*5, 252=2^2*3^2*7, 264=2^3*3*11, 270=2*3^3*5

Mathematica

f[n_]:=Sort[Last/@FactorInteger[n]]=={1, 1, 3} || Sort[Last/@FactorInteger[n]]=={1, 2, 2}; Select[Range[2000], f]

Prog

(PARI) list(lim)=my(v=List(), t); forprime(p=2, (lim\6)^(1/3), forprime(q=2, sqrt(lim\p^3), if(p==q, next); t=p^3*q; forprime(r=q+1, lim\t, if(p==r, next); listput(v, t*r)))); 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

Union of A189975 and A179643.

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

Sequence in context: A034291 A039602 A316835 * A099832 A111399 A030634

Adjacent sequences: A179639 A179640 A179641 * A179643 A179644 A179645

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Jul 21 2010

Status

approved