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A345747 a(n) = n! * Sum_{k=0..floor(n/2)} k^(n - 2*k)/k!. 2
1, 0, 2, 6, 36, 240, 2280, 27720, 425040, 7862400, 171188640, 4319330400, 125199708480, 4142318019840, 155388782989440, 6557345831836800, 308677784640825600, 16079233115648102400, 920518264903690252800, 57603377545940850624000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..19.

FORMULA

E.g.f.: Sum_{k>=0} x^(2*k) / (k! * (1 - k * x)).

PROG

(PARI) a(n) = n!*sum(k=0, n\2, k^(n-2*k)/k!);

(PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(sum(k=0, N, x^(2*k)/(k!*(1-k*x)))))

CROSSREFS

Cf. A354436, A355575.

Cf. A104872.

Sequence in context: A052845 A052832 A058583 * A075096 A347897 A354413

Adjacent sequences:  A345744 A345745 A345746 * A345748 A345749 A345750

KEYWORD

nonn

AUTHOR

Seiichi Manyama, Sep 17 2022

STATUS

approved

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Last modified October 3 07:14 EDT 2022. Contains 357231 sequences. (Running on oeis4.)