A038541 a(n) = number of modules with n elements over the ring of integers in the imaginary quadratic field of discriminant -20.

1, 1, 2, 2, 1, 2, 2, 3, 5, 1, 0, 4, 0, 2, 2, 5, 0, 5, 0, 2, 4, 0, 2, 6, 2, 0, 10, 4, 2, 2, 0, 7, 0, 0, 2, 10, 0, 0, 0, 3, 2, 4, 2, 0, 5, 2, 2, 10, 5, 2, 0, 0, 0, 10, 0, 6, 0, 2, 0, 4, 2, 0, 10, 11, 0, 0, 2, 0, 4, 2, 0, 15, 0, 0, 4, 0, 0, 0, 0, 5, 20, 2, 2, 8, 0, 2, 4, 0, 2, 5, 0, 4, 0, 2, 0, 14

Offset: 1

Author

Paolo Dominici (pl.dm(AT)libero.it)

Keywords

• nonn
• mult

Comments

Equivalently, number of modules with n elements over the ring Z[sqrt(-5)].

See A352550 for comments and PARI code.

Crossrefs

Cf. A038540, A038541, A248107, A352550-A352567.

Extensions

Edited by M. F. Hasler, Feb 18 2022

Revised by N. J. A. Sloane, Mar 21 2022