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

Author

Benoit Cloitre, Apr 06 2003

Keywords

• nonn

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

Examples

			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.
		

Links

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

Crossrefs

Cf. A000364, A045326.

Formula

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

Extensions

More terms from Hakan Icoz, Sep 06 2020