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A336426
Numbers that cannot be written as a product of superprimorials {2, 12, 360, 75600, ...}.
14
3, 5, 6, 7, 9, 10, 11, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 28, 29, 30, 31, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76
OFFSET
1,1
COMMENTS
The n-th superprimorial is A006939(n) = Product_{i = 1..n} prime(i)^(n - i + 1).
EXAMPLE
We have 288 = 2*12*12 so 288 is not in the sequence.
MATHEMATICA
chern[n_]:=Product[Prime[i]^(n-i+1), {i, n}];
facsusing[s_, n_]:=If[n<=1, {{}}, Join@@Table[(Prepend[#, d]&)/@Select[facsusing[Select[s, Divisible[n/d, #]&], n/d], Min@@#>=d&], {d, Select[s, Divisible[n, #]&]}]];
Select[Range[100], facsusing[Array[chern, 30], #]=={}&]
CROSSREFS
A181818 is the complement.
A336497 is the version for superfactorials.
A001055 counts factorizations.
A006939 lists superprimorials or Chernoff numbers.
A022915 counts permutations of prime indices of superprimorials.
A317829 counts factorizations of superprimorials.
A336417 counts perfect-power divisors of superprimorials.
Sequence in context: A254614 A320698 A182834 * A336497 A116883 A256543
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jul 26 2020
STATUS
approved