This site is supported by donations to The OEIS Foundation.

The OEIS is looking to hire part-time people to help edit core sequences, upload scanned documents, process citations, fix broken links, etc. - Neil Sloane, njasloane@gmail.com

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A084227 Numbers of the form p*q^k with distinct primes p and q, k>0. 3
 6, 10, 12, 14, 15, 18, 20, 21, 22, 24, 26, 28, 33, 34, 35, 38, 39, 40, 44, 45, 46, 48, 50, 51, 52, 54, 55, 56, 57, 58, 62, 63, 65, 68, 69, 74, 75, 76, 77, 80, 82, 85, 86, 87, 88, 91, 92, 93, 94, 95, 96, 98, 99, 104, 106, 111, 112, 115, 116, 117, 118, 119, 122, 123, 124, 129 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A001221(a(n)) = 2; A001222(a(n)) = A051903(a(n)) + 1. LINKS G. C. Greubel, Table of n, a(n) for n = 1..1000 FORMULA a(n) ~ n log n/log log n. - Charles R Greathouse IV, Oct 19 2015 EXAMPLE 80 = 5*2^4, therefore 80 is a term. MATHEMATICA doit[{p_, q_}]:=Table[{p q^k, q p^k}, {k, 10}]; Take[Union[Flatten[ doit/@ Subsets[Prime[Range[20]], {2}]]], 70] (* Harvey P. Dale, May 09 2012 *) PROG (PARI) is(n)=my(f=factor(n)[, 2]); #f==2 && vecmin(f)==1 \\ Charles R Greathouse IV, Oct 19 2015 CROSSREFS Cf. A000961, A006881. Sequence in context: A267114 A275665 A056760 * A237051 A100658 A182301 Adjacent sequences:  A084224 A084225 A084226 * A084228 A084229 A084230 KEYWORD nonn AUTHOR Reinhard Zumkeller, May 20 2003 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.