OFFSET
1,2
FORMULA
a(n) = a(n-1)+4*a(n-2)-4*a(n-3)-6*a(n-4)+6*a(n-5)+4*a(n-6)-4*a(n-7)-a(n-8)+a(n-9). G.f.: x*(-1-x-23*x^2+3*x^3-23*x^4-3*x^5-x^6+x^7)/((1+x)^4*(x-1)^5). [R. J. Mathar, Feb 22 2009]
MATHEMATICA
a = {}; r = 3; s = 0; Do[k = 0; Do[k = k + (Sin[Pi m/2]^2) m^r + (Cos[Pi m/2]^2) m^s, {m, 1, n}]; AppendTo[a, k], {n, 1, 100}]; a (*Artur Jasinski*)
nxt[{a_, b_}]:={a+1, If[EvenQ[a], b+(a+1)^3, b+1]}; Transpose[NestList[nxt, {1, 1}, 40]][[2]] (* Harvey P. Dale, Dec 13 2011 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Artur Jasinski, May 12 2008
STATUS
approved