A140146 a(1)=1, a(n)=a(n-1)+n^1 if n odd, a(n)=a(n-1)+ n^4 if n is even.

1, 17, 20, 276, 281, 1577, 1584, 5680, 5689, 15689, 15700, 36436, 36449, 74865, 74880, 140416, 140433, 245409, 245428, 405428, 405449, 639705, 639728, 971504, 971529, 1428505, 1428532, 2043188, 2043217, 2853217, 2853248, 3901824, 3901857

Offset: 1

Author

Artur Jasinski, May 12 2008

Keywords

• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000027, A000217, A000330, A000537, A000538, A000539, A136047, A140113.

Programs

Mathematica

a = {}; r = 1; s = 4; 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[{n_,a_}]:={n+1,If[OddQ[n+1],a+n+1,a+(n+1)^4]}; Transpose[NestList[nxt,{1,1},40]][[2]] (* Harvey P. Dale, Mar 19 2013 *)

Formula

G.f.: -x*(x^2+1)*(x^6-16*x^5-3*x^4-160*x^3+3*x^2-16*x-1)/((1+x)^5*(x-1)^6). [From R. J. Mathar, Feb 22 2009]