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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

Table of n, a(n) for n=1..13.

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

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Last modified December 8 08:56 EST 2021. Contains 349594 sequences. (Running on oeis4.)