A081727 Length of periods of Euler numbers modulo n.

1, 1, 2, 1, 2, 2, 6, 4, 6, 2, 10, 2, 6, 6, 2, 8, 8, 6, 18, 2, 6, 10, 22, 4, 10, 6, 18, 6, 14, 2, 30, 16, 10, 8, 6, 6, 18, 18, 6, 4, 20, 6, 42, 10, 6, 22, 46, 8, 42, 10, 8, 6, 26, 18, 10, 12, 18, 14, 58, 2, 30, 30, 6, 32, 6, 10, 66, 8, 22, 6, 70, 12, 36, 18, 10

Offset

1,3

Comments

Terms after a(126) need more Euler numbers to check the period length. There are 85 unknown terms starting from a(127) till a(500) when 242 Euler numbers are used. - Hakan Icoz, Sep 06 2020

Links

Hakan Icoz, Table of n, a(n) for n = 1..125

Formula

a(n) = n-1 if n=2, 3, 7, 11, 19, 23, 31...is a prime == 2 or 3 (mod 4) (A045326).

Example

A000364 modulo 5 gives : 1,1,0,1,0,1,0,1,0,1,0,... with period (1,0) of length 2, hence a(5)=2.

Crossrefs

Cf. A000364, A045326.

Sequence in context: A054706 A351082 A334500 * A000020 A077014 A093655

Adjacent sequences: A081724 A081725 A081726 * A081728 A081729 A081730

Keyword

nonn

Author

Benoit Cloitre, Apr 06 2003

Extensions

More terms from Hakan Icoz, Sep 06 2020

Status

approved