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

0,2

Links

Table of n, a(n) for n=0..21.

Formula

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

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

Mathematica

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

Crossrefs

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

Sequence in context: A124453 A211827 A360582 * A322339 A000165 A241122

Adjacent sequences: A375486 A375487 A375488 * A375490 A375491 A375492

Keyword

nonn,base,easy

Author

Stefano Spezia, Aug 18 2024

Status

approved