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A022560 a(0)=0, a(2*n) = 2*a(n) +2*a(n-1) +n^2 +n, a(2*n+1) = 4*a(n) +(n+1)^2. 4
0, 1, 4, 8, 16, 25, 36, 48, 68, 89, 112, 136, 164, 193, 224, 256, 304, 353, 404, 456, 512, 569, 628, 688, 756, 825, 896, 968, 1044, 1121, 1200, 1280, 1392, 1505, 1620, 1736, 1856, 1977, 2100, 2224, 2356, 2489, 2624, 2760, 2900, 3041 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..5000

R. Stephan, Some divide-and-conquer sequences ...

R. Stephan, Table of generating functions

FORMULA

Let a(i, n) = 2^(i-1)*floor(1/2 + n/2^i); sequence is a(n) = Sum_{i=1} a(i, n)*(n - a(i, n)).

Second differences give A006519.

Also a(1)=0 and a(n) = floor(n^2/4) + a(floor(n/2)) + a(ceil(n/2)).

G.f.: 1/(1-x)^2 * (x/(1-x) + Sum(k>=1, 2^(k-1)*x^2^k/(1-x^2^k))). - Ralf Stephan, Apr 17 2003

a(0)=0, a(2n) = 2a(n)+2a(n-1)+n^2+n, a(2n+1) = 4a(n)+(n+1)^2. - Ralf Stephan, Sep 13 2003

MATHEMATICA

a[0]:= 0; a[1]:= 1; a[n_]:= If[n == 0, 0, If[Mod[n, 2] == 0, 2*a[n/2] + 2*a[n/2 - 1] + (n/2)^2 + (n/2), 4*a[(n - 1)/2] + ((n + 1)/2)^2]];

Table[a[n], {n, 0, 50}] (* G. C. Greubel, Feb 26 2018 *)

PROG

(PARI) a(n) = if (n==0, 0, if (n % 2, my(nn = (n-1)/2); 4*a(nn)+(nn+1)^2, my(nn = n/2); 2*a(nn)+2*a(nn-1)+nn^2+nn)) \\ Michel Marcus, Jun 27 2013

CROSSREFS

First differences are in A006520.

Cf. A070263.

Sequence in context: A222089 A246067 A161226 * A290190 A193452 A003451

Adjacent sequences:  A022557 A022558 A022559 * A022561 A022562 A022563

KEYWORD

nonn

AUTHOR

Andre Kundgen (kundgen(AT)math.uiuc.edu)

EXTENSIONS

More terms from Ralf Stephan, Sep 13 2003

STATUS

approved

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Last modified August 21 13:31 EDT 2018. Contains 313954 sequences. (Running on oeis4.)