

A006939


Chernoff sequence: a(n) = Product_{k=1..n} prime(k)^(nk+1).
(Formerly M2050)


107



1, 2, 12, 360, 75600, 174636000, 5244319080000, 2677277333530800000, 25968760179275365452000000, 5793445238736255798985527240000000, 37481813439427687898244906452608585200000000, 7517370874372838151564668004911177464757864076000000000, 55784440720968513813368002533861454979548176771615744085560000000000
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OFFSET

0,2


COMMENTS

Product of first n primorials: a(n) = Product_{i=1..n} A002110(i).
Superprimorials, from primorials by analogy with superfactorials.
Smallest number k with n distinct exponents in its prime factorization, i.e., A071625(k) = n.
This might be a good place to explain the name "Chernoff sequence" since his name does not appear in the References or Links as of Mar 22 2014.  Jonathan Sondow, Mar 22 2014
Pickover (1992) named this sequence after Paul Chernoff of California who contributed this sequence to his book. He was possibly referring to American mathematician Paul Robert Chernoff (1942  2017), a professor at the University of California.  Amiram Eldar, Jul 27 2020


REFERENCES

Clifford A. Pickover, Mazes for the Mind, St. Martin's Press, NY, 1992, p. 351.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
James K. Strayer, Elementary number theory, Waveland Press, Inc., Long Grove, IL, 1994. See p. 37.


LINKS



FORMULA

a(n) = m(1)*m(2)*m(3)*...*m(n), where m(n) = nth primorial number.  N. J. A. Sloane, Feb 20 2005
a(0) = 1, a(n) = a(n  1)p(n)#, where p(n)# is the nth primorial A002110(n) (the product of the first n primes).  Alonso del Arte, Sep 30 2011


EXAMPLE

a(4) = 360 because 2^3 * 3^2 * 5 = 1 * 2 * 6 * 30 = 360.
a(5) = 75600 because 2^4 * 3^3 * 5^2 * 7 = 1 * 2 * 6 * 30 * 210 = 75600.


MAPLE

a := []; printlevel := 1; for k from 0 to 20 do a := [op(a), product(ithprime(i)^(ki+1), i=1..k)] od; print(a);


MATHEMATICA

Rest[FoldList[Times, 1, FoldList[Times, 1, Prime[Range[15]]]]] (* Harvey P. Dale, Jul 07 2011 *)
Table[Times@@Table[Prime[i]^(n  i + 1), {i, n}], {n, 12}] (* Alonso del Arte, Sep 30 2011 *)


PROG

(Haskell)
a006939 n = a006939_list !! n
(Magma) [1] cat [(&*[NthPrime(k)^(nk+1): k in [1..n]]): n in [1..15]]; // G. C. Greubel, Oct 14 2018


CROSSREFS

Cf. A000178 (product of first n factorials), A007489 (sum of first n factorials), A060389 (sum of first n primorials).
A000142 counts divisors of superprimorials.
A000325 counts uniform divisors of superprimorials.
A008302 counts divisors of superprimorials by bigomega.
A022915 counts permutations of prime indices of superprimorials.
A118914 has row a(n) equal to {1..n}.
A124010 has row a(n) equal to {n..1}.
A130091 lists numbers with distinct prime multiplicities.
A317829 counts factorizations of superprimorials.
A336417 counts perfectpower divisors of superprimorials.
A336426 gives nonproducts of superprimorials.


KEYWORD

easy,nonn,nice


AUTHOR



EXTENSIONS



STATUS

approved



