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Omit the trailing zeros from double factorial of even numbers (A000165).
0

%I #12 Aug 18 2024 20:29:17

%S 1,2,8,48,384,384,4608,64512,1032192,18579456,37158912,817496064,

%T 19619905536,510117543936,14283291230208,42849873690624,

%U 1371195958099968,46620662575398912,1678343852714360832,63777066403145711616,255108265612582846464,10714547155728479551488

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

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

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

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

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

%K nonn,base,easy

%O 0,2

%A _Stefano Spezia_, Aug 18 2024