OFFSET
0,2
FORMULA
a(n+1) = (2^(n + 1) + 1)*a(n) - 2^n*a(n - 1) + 1.
a(n+1) = ((a(n - 2) + 4*a(n - 1) + 4)*a(n) - 2*a(n - 1)^2 - 4*a(n)^2 + a(n - 2) - 4*a(n - 1))/(a(n - 2) - 2*a(n - 1)).
a(n) = 2^(n*(n+1)/2) + sum_{k=1..n} 2^( (n+k+1)*(n-k)/2 ) * k. - Max Alekseyev, Sep 05 2010
MATHEMATICA
nxt[{n_, a_}]:={n+1, a*2^(n+1)+n+1}; Transpose[NestList[nxt, {0, 1}, 20]] [[2]] (* Harvey P. Dale, Apr 05 2015 *)
PROG
(PARI) a(n)=if(n<=0, 1, a(n-1)*2^n+n )
CROSSREFS
KEYWORD
nonn
AUTHOR
Georgi Guninski, Sep 05 2010
EXTENSIONS
Minor edits by N. J. A. Sloane, Sep 05 2010
STATUS
approved