A056921 a(0) = 0, a(1) = 1, a(2*n) = n*a(2*n-1) + a(2*n-2), a(2*n+1) = a(2*n) + a(2*n-1).

0, 1, 1, 2, 5, 7, 26, 33, 158, 191, 1113, 1304, 8937, 10241, 80624, 90865, 807544, 898409, 8893225, 9791634, 106809565, 116601199, 1389422754, 1506023953, 19461710190, 20967734143, 292042254049, 313009988192, 4674182088737

Offset

0,4

Comments

Conjecture: for n >= 1, a(n-1) is not divisible by n, except at n=5 (verified for n <= 10^7). - Davide Oliveri, Oct 03 2025

Links

Seiichi Manyama, Table of n, a(n) for n = 0..897

Formula

Numerators of continued fraction for alternating factorial.

Crossrefs

Cf. A058797, A361938.

Sequence in context: A188499 A215535 A383504 * A041245 A042159 A071898

Adjacent sequences: A056918 A056919 A056920 * A056922 A056923 A056924

Keyword

frac,easy,nonn

Author

Aleksandar Petojevic, Sep 05 2000

Extensions

More terms from James Sellers, Sep 07 2000

Status

approved