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A027412 a(n) = 2*a(n-1) + (n-2)*a(n-2). 2
1, 2, 4, 10, 28, 86, 284, 998, 3700, 14386, 58372, 246218, 1076156, 4860710, 22635292, 108459814, 533813716, 2694524642, 13930068740, 73667056394, 398075350108, 2195824771702, 12353156545564, 70818633296870 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..200

R. Donaghey, Binomial self-inverse sequences and tangent coefficients, J. Combin. Theory, Series A, 21 (1976), 155-163.

FORMULA

a(n) ~ sqrt(2)*exp(2*sqrt(n)-n/2-1)*n^(n/2-1/2). - Vaclav Kotesovec, Oct 08 2012

MATHEMATICA

RecurrenceTable[{a[0]==1, a[1]==2, a[n]==2 a[n-1] + (n-2) a[n-2]}, a, { n, 40}] (* Vincenzo Librandi, Dec 29 2012 *)

CROSSREFS

a(n) = 2 * A005425(n-1), n>0.

Sequence in context: A149830 A272484 A253409 * A030277 A149831 A149832

Adjacent sequences:  A027409 A027410 A027411 * A027413 A027414 A027415

KEYWORD

nonn,easy

AUTHOR

Olivier Gérard

STATUS

approved

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Last modified February 16 14:47 EST 2019. Contains 320163 sequences. (Running on oeis4.)