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A309965
a(n) is the greatest product of the digits of n in any base b in the range 2..n.
2
0, 1, 1, 2, 2, 3, 4, 4, 4, 6, 5, 6, 8, 9, 8, 10, 9, 12, 12, 10, 12, 15, 16, 14, 16, 18, 16, 20, 18, 21, 20, 20, 24, 25, 20, 22, 24, 28, 25, 30, 27, 30, 32, 27, 30, 35, 36, 36, 33, 36, 35, 40, 40, 42, 36, 36, 40, 45, 36, 42, 48, 49, 48, 50, 45, 48, 48, 54, 50
OFFSET
2,4
FORMULA
a(n) < n.
EXAMPLE
For n = 8:
- the digits of 8 in bases b = 2..8 and the corresponding products are:
b digits product
- ------ -------
2 "1000" 0
3 "22" 4
4 "20" 0
5 "13" 3
6 "12" 2
7 "11" 1
8 "10" 0
- hence a(8) = 4.
PROG
(PARI) a(n) = vecmax(vector(n-1, b, vecprod(digits(n, b+1))))
CROSSREFS
See A309969 for the corresponding base b.
Cf. A007954.
Sequence in context: A262976 A349608 A224709 * A366385 A070172 A273353
KEYWORD
nonn,base
AUTHOR
Rémy Sigrist, Aug 25 2019
STATUS
approved