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Double Factorial -- from Wolfram MathWorld

The double factorial of a positive integer n is a generalization of the usual factorial n! defined by n!!={n·(n-2)...5·3·1 n>0 odd; n·(n-2)...6·4·2 n>0 even; 1 n=-1,0. (1) Note that -1!!=0!!=1, by definition (Arfken 1985, p. 547). The origin of the notation n!! appears not to not be widely known and is not mentioned in Cajori (1993). For n=0, 1, 2, ..., the first few values are 1, 1, 2, 3, 8, 15, 48, 105, 384, ... (OEIS A006882). The numbers of...



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Double Factorial -- from Wolfram MathWorld

https://mathworld.wolfram.com/DoubleFactorial.html

The double factorial of a positive integer n is a generalization of the usual factorial n! defined by n!!={n·(n-2)...5·3·1 n>0 odd; n·(n-2)...6·4·2 n>0 even; 1 n=-1,0. (1) Note that -1!!=0!!=1, by definition (Arfken 1985, p. 547). The origin of the notation n!! appears not to not be widely known and is not mentioned in Cajori (1993). For n=0, 1, 2, ..., the first few values are 1, 1, 2, 3, 8, 15, 48, 105, 384, ... (OEIS A006882). The numbers of...



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https://mathworld.wolfram.com/DoubleFactorial.html

Double Factorial -- from Wolfram MathWorld

The double factorial of a positive integer n is a generalization of the usual factorial n! defined by n!!={n·(n-2)...5·3·1 n>0 odd; n·(n-2)...6·4·2 n>0 even; 1 n=-1,0. (1) Note that -1!!=0!!=1, by definition (Arfken 1985, p. 547). The origin of the notation n!! appears not to not be widely known and is not mentioned in Cajori (1993). For n=0, 1, 2, ..., the first few values are 1, 1, 2, 3, 8, 15, 48, 105, 384, ... (OEIS A006882). The numbers of...

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      Double Factorial -- from Wolfram MathWorld
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      The double factorial of a positive integer n is a generalization of the usual factorial n! defined by n!!={n·(n-2)...5·3·1 n>0 odd; n·(n-2)...6·4·2 n>0 even; 1 n=-1,0. (1) Note that -1!!=0!!=1, by definition (Arfken 1985, p. 547). The origin of the notation n!! appears not to not be widely known and is not mentioned in Cajori (1993). For n=0, 1, 2, ..., the first few values are 1, 1, 2, 3, 8, 15, 48, 105, 384, ... (OEIS A006882). The numbers of...
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      The double factorial of a positive integer n is a generalization of the usual factorial n! defined by n!!={n·(n-2)...5·3·1 n>0 odd; n·(n-2)...6·4·2 n>0 even; 1 n=-1,0. (1) Note that -1!!=0!!=1, by definition (Arfken 1985, p. 547). The origin of the notation n!! appears not to not be widely known and is not mentioned in Cajori (1993). For n=0, 1, 2, ..., the first few values are 1, 1, 2, 3, 8, 15, 48, 105, 384, ... (OEIS A006882). The numbers of...

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      Double Factorial -- from Wolfram MathWorld
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      The double factorial of a positive integer n is a generalization of the usual factorial n! defined by n!!={n·(n-2)...5·3·1 n>0 odd; n·(n-2)...6·4·2 n>0 even; 1 n=-1,0. (1) Note that -1!!=0!!=1, by definition (Arfken 1985, p. 547). The origin of the notation n!! appears not to not be widely known and is not mentioned in Cajori (1993). For n=0, 1, 2, ..., the first few values are 1, 1, 2, 3, 8, 15, 48, 105, 384, ... (OEIS A006882). The numbers of...

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      The double factorial of a positive integer n is a generalization of the usual factorial n! defined by n!!={n·(n-2)...5·3·1 n>0 odd; n·(n-2)...6·4·2 n>0 even; 1 n=-1,0. (1) Note that -1!!=0!!=1, by definition (Arfken 1985, p. 547). The origin of the notation n!! appears not to not be widely known and is not mentioned in Cajori (1993). For n=0, 1, 2, ..., the first few values are 1, 1, 2, 3, 8, 15, 48, 105, 384, ... (OEIS A006882). The numbers of...
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