The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified April 15 00:44 EDT 2021. Contains 342971 sequences. (Running on oeis4.)