The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A114426 Product of the first n 4-almost primes (A014613). 5
 16, 384, 13824, 552960, 29859840, 1672151040, 100329062400, 8126654054400, 682638940569600, 60072226770124800, 5406500409311232000, 540650040931123200000, 56227604256836812800000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 4-almost prime analog of primorial (A002110). The semiprime analog of primorial is A112141. Equivalent for product of what A086046 is for sum. Bigomega(a(n)) = the number of not necessarily distinct prime factors of a(n) = A001222(a(n)) = A008586(n) = 4*n. LINKS FORMULA a(n) = Prod[from i = 1 to n] A014613(i). EXAMPLE a(5) = 29859840 = 16 * 24 * 36 * 40 * 54 = the product of the first 5 values of the 4-almost primes = 2^13 * 3^6 * 5, which has 4*5 = 20 prime factors (with multiplicity). MATHEMATICA FoldList[Times, Select[Range[200], PrimeOmega[#]==4&]] (* Harvey P. Dale, Dec 02 2018 *) CROSSREFS Cf. A001222, A002110, A008585, A014613, A008586, A086046, A112141. Sequence in context: A303466 A116166 A034976 * A189849 A051360 A227390 Adjacent sequences:  A114423 A114424 A114425 * A114427 A114428 A114429 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 December 8 08:56 EST 2021. Contains 349594 sequences. (Running on oeis4.)