A375489 Omit the trailing zeros from double factorial of even numbers (A000165).

1, 2, 8, 48, 384, 384, 4608, 64512, 1032192, 18579456, 37158912, 817496064, 19619905536, 510117543936, 14283291230208, 42849873690624, 1371195958099968, 46620662575398912, 1678343852714360832, 63777066403145711616, 255108265612582846464, 10714547155728479551488

Offset: 0

Author

Stefano Spezia, Aug 18 2024

Keywords

• nonn
• base
• easy

Crossrefs

Cf. A000165, A004154, A005843, A011557, A027868, A122840, A358987.

Programs

Mathematica

a[n_]:=2^n*n!/10^IntegerExponent[n!,10]; Array[a,22,0]

Formula

a(n) = A000165(n)/10^A027868(n).

a(n) = a(n-1)*(2*n)/10^A122840(2*n) for n > 0.