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A286307 a(n) is the numerator of r(n), where r(n) = r(n-1) + r(n-2)/(2*(n-1)) with r(0) = 0, r(1) = 1. 2
0, 1, 1, 5, 17, 151, 823, 10631, 15871, 1344097, 12731713, 266731133, 3061359593, 15281334539, 1030023060151, 29833932429263, 461929309281059, 15229246883432833, 53257613193371021, 9845267571825141941, 191853269052081088769, 462422990938113014567, 168922073145947967975799 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Robert Israel, Table of n, a(n) for n = 0..426

FORMULA

From Wolfdieter Lang, Jun 07 2017: (Start)

G.f. of {r(n)}_{n>=0}: x*exp(-x/2)/(1-x)^(3/2).

a(n) = numerator(r(n)). See the name for the recurrence of r(n). (End)

MAPLE

R[0]:= 0: R[1]:= 1: A[0]:= 0: A[1]:= 1:

for n from 2 to 30 do

  R[n]:= R[n-1] + R[n-2]/(2*(n-1));

  A[n]:= numer(R[n]);

od:

seq(A[i], i=0..30); # Robert Israel, May 25 2017

MATHEMATICA

Numerator[RecurrenceTable[{r[n] == r[n - 1] + r[n - 2]/(2 (n - 1)), r[0] == 0, r[1] == 1}, r, {n, 0, 25}]]

PROG

(PARI) a(n) = if(n < 2, return(n)); n++; my(v=vector(n)); v[1]=0; v[2] = 1; for(i = 3, n, v[i] = v[i-1] + v[i-2]/(2*i - 4)); numerator(v[#v]) \\ David A. Corneth, May 14 2017

CROSSREFS

Cf. A019609, A268363.

Sequence in context: A177509 A160611 A281429 * A119769 A182066 A090886

Adjacent sequences:  A286304 A286305 A286306 * A286308 A286309 A286310

KEYWORD

nonn,easy

AUTHOR

Terry D. Grant, May 05 2017

EXTENSIONS

Name changed, a(0) and a(1) added by David A. Corneth, May 14 2017

a(20)-a(22) from David A. Corneth, May 21 2017

Name corrected by Robert Israel, May 25 2017

STATUS

approved

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Last modified October 22 09:31 EDT 2019. Contains 328315 sequences. (Running on oeis4.)