A056129 - OEIS

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A056129

Final nonzero digit of n-th primorial.

1, 2, 6, 3, 1, 1, 3, 1, 9, 7, 3, 3, 1, 1, 3, 1, 3, 7, 7, 9, 9, 7, 3, 9, 1, 7, 7, 1, 7, 3, 9, 3, 3, 1, 9, 1, 1, 7, 1, 7, 1, 9, 9, 9, 7, 9, 1, 1, 3, 1, 9, 7, 3, 3, 3, 1, 3, 7, 7, 9, 9, 7, 1, 7, 7, 1, 7, 7, 9, 3, 7, 1, 9, 3, 9, 1, 3, 7, 9, 9, 1, 9, 9, 9, 7, 3, 9, 1, 7, 7, 1, 7, 3, 1, 1, 9, 7, 3, 3, 9, 9

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OFFSET

0,2

COMMENTS

For n > 2, a(n) is in {1, 3, 7, 9}.

LINKS

Table of n, a(n) for n=0..100.

Index entries for sequences related to final digits of numbers

FORMULA

a(n) = prime(n)#/10 mod 10 for n > 2. - Charles R Greathouse IV, Dec 03 2024

MATHEMATICA

Do[p = Product[Prime[m], {m, 1, n}]; While[Mod[p, 10] == 0, p = p/10]; Print[Mod[p, 10]], {n, 0, 100}]