A091835 Double factorial of primes.

2, 3, 15, 105, 10395, 135135, 34459425, 654729075, 316234143225, 6190283353629375, 191898783962510625, 8200794532637891559375, 13113070457687988603440625, 563862029680583509947946875, 1192568192774434123539907640625, 157952079428395476360490147277859375

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..140

Formula

a(n) = prime(n)!!.

Example

a(2) = 3 because 3*1 = 3;
a(3) = 15 because 5*3*1 = 15;
......

Maple

a:= n-> doublefactorial(ithprime(n)):
seq(a(n), n=1..20);  # Alois P. Heinz, Jul 24 2017

Mathematica

Table[ Prime[n]!!, {n, 14}]

Prog

(Magma) DoubleFactorial:=func< n | &*[n..2 by -2] >; [ DoubleFactorial(NthPrime(n)): n in [1..16] ]; // Vincenzo Librandi, Jul 24 2017

Crossrefs

Cf. A001147, A006882.

Sequence in context: A238711 A362999 A165657 * A131612 A297421 A180723

Adjacent sequences: A091832 A091833 A091834 * A091836 A091837 A091838

Keyword

nonn,easy

Author

Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Mar 09 2004

Extensions

More terms from Robert G. Wilson v, Mar 11 2004

Status

approved