OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..30
J. Overbey, W. Traves and J. Wojdylo, On the Keyspace of the Hill Cipher.
FORMULA
a(n) = (9^n - 1)*(9^n - 9)*...*(9^n - 9^(n-1)).
MATHEMATICA
Table[Product[(9^n - 9^j), {j, 0, n-1}], {n, 0, 10}] (* G. C. Greubel, May 14 2019 *)
PROG
(Magma) [1] cat [&*[(9^n - 9^k): k in [0..n-1]]: n in [1..10]]; // Bruno Berselli, Jan 28 2013
(PARI) {a(n) = prod(j=0, n-1, 9^n - 9^j)}; \\ G. C. Greubel, May 14 2019
(Sage) [product(9^n - 9^j for j in (0..n-1)) for n in (0..10)] # G. C. Greubel, May 14 2019
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vladeta Jovovic, Mar 16 2000
STATUS
approved