The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation. Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A114425 Product of the first n 3-almost primes (A014612). 2
 8, 96, 1728, 34560, 933120, 26127360, 783820800, 32920473600, 1448500838400, 65182537728000, 3259126886400000, 169474598092800000, 10676899679846400000, 704675378869862400000, 47917925763150643200000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 3-almost prime analog of primorial (A002110). The semiprime analog of primorial is A112141. Equivalent for product of what A086062 is for sum. Bigomega(a(n)) = the number of not necessarily distinct prime factors of a(n) = A001222(a(n)) = A008585(n) = 3*n. LINKS Harvey P. Dale, Table of n, a(n) for n = 1..364 FORMULA a(n) = Prod[from i = 1 to n] A014612(i). EXAMPLE a(5) = 933120 = 8 * 12 * 18 * 20 * 27 = the product of the first 5 values of the 3-almost primes = 2^8 * 3^6 * 5, which has 3*5 = 15 prime factors (with multiplicity). a(20) = 137199755075271237225676800000000 = 8 * 12 * 18 * 20 * 27 * 28 * 30 * 42 * 44 * 45 * 50 * 52 * 63 * 66 * 68 * 70 * 75 * 76 * 78 * 92 = 2^26 * 3^15 * 5^8 * 7^4 * 11, which has 20*3 = 60 prime factors (with multiplicity). MATHEMATICA FoldList[Times, Select[Range, PrimeOmega[#]==3&]] (* Harvey P. Dale, Apr 26 2020 *) CROSSREFS Cf. A002110, A008585, A014612, A086062, A112141. Sequence in context: A034177 A052570 A002168 * A224767 A337597 A052127 Adjacent sequences:  A114422 A114423 A114424 * A114426 A114427 A114428 KEYWORD easy,nonn AUTHOR Jonathan Vos Post, Feb 13 2006 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
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified November 23 14:26 EST 2020. Contains 338590 sequences. (Running on oeis4.)