OFFSET
0,2
LINKS
Altug Alkan, Table of n, a(n) for n = 0..1000
FORMULA
a(n) = 2 * floor(e^(1/2) * n! * 2^n) - 2n - 2.
E.g.f.: (2x+4x^2)/(1-2x) * exp(x).
a(n) = 2*A271476(n) for n >= 1. - Altug Alkan, Aug 01 2018
MATHEMATICA
RecurrenceTable[{a[0]==0, a[n]==(a[n-1]+2n-1)2n}, a, {n, 20}] (* Harvey P. Dale, May 20 2014 *)
PROG
(PARI) a(n)=2*floor(exp(1/2)*n!*2^n)-2*n-2
(PARI) x='x+O('x^99); concat(0, Vec(serlaplace((2*x+4*x^2)/(1-2*x)*exp(x)))) \\ Altug Alkan, Aug 01 2018
(PARI) a=vector(99); a[1]=2; for(n=2, #a, a[n] = 2*(a[n-1]+2*n-1)*n); concat(0, a) \\ Altug Alkan, Aug 01 2018
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Emrehan Halici (emrehan(AT)halici.com.tr), Apr 24 2004
EXTENSIONS
Edited by Ralf Stephan, Apr 26 2004
STATUS
approved