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A294039 a(n) = e*Gamma(2*n,1). 3
2, 16, 326, 13700, 986410, 108505112, 16926797486, 3554627472076, 966858672404690, 330665665962404000, 138879579704209680022, 70273067330330098091156, 42163840398198058854693626, 29599015959535037315994925480, 24034400959142450300587879489790 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..225

FORMULA

From Robert Israel, Nov 14 2017: (Start)

a(n) = (2*n-1)!*Sum_{k=0..2*n-1} 1/k!.

a(n+1) = 2*n*(2*n+1)*a(n) + 2*n+2. (End)

MAPLE

a := n -> exp(1)*GAMMA(2*n, 1):

seq(simplify(a(n)), n=1..15);

# Alternate:

f:= gfun:-rectoproc({a(n+1) = 2*n*(2*n+1)*a(n) + 2*n+2, a(1) = 2}, a(n), remember):

map(f, [$1..20]); # Robert Israel, Nov 14 2017

MATHEMATICA

Array[E Gamma[2 #, 1] &, 15] (* Michael De Vlieger, Nov 14 2017 *)

CROSSREFS

Bisection of A000522. Cf. A294040.

Sequence in context: A171212 A282392 A336522 * A009100 A009109 A268560

Adjacent sequences:  A294036 A294037 A294038 * A294040 A294041 A294042

KEYWORD

nonn

AUTHOR

Peter Luschny, Nov 14 2017

STATUS

approved

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Last modified November 26 13:27 EST 2022. Contains 358362 sequences. (Running on oeis4.)