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A028569 n(n+9). 15
0, 10, 22, 36, 52, 70, 90, 112, 136, 162, 190, 220, 252, 286, 322, 360, 400, 442, 486, 532, 580, 630, 682, 736, 792, 850, 910, 972, 1036, 1102, 1170, 1240, 1312, 1386, 1462, 1540, 1620, 1702, 1786, 1872, 1960, 2050, 2142, 2236, 2332, 2430 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..45.

P. De Geest, Palindromic Quasipronics of the form n(n+x)

FORMULA

Equals 2*A056000 - Zerinvary Lajos, Feb 12 2007

a(n)=2*n+a(n-1)+8. [From Vincenzo Librandi, Aug 05 2010]

sum_{n>=1} 1/a(n) = 7129/22680 = 0.314329806... - R. J. Mathar, Mar 22 2011

G.f.: 2*x*(5-4*x)/(1-x)^3. [Colin Barker, Jan 10 2012]

MAPLE

with(finance):seq(add(cashflows([2, k, k], 0 ), k=4..n), n=3..51); - Zerinvary Lajos, Jun 30 2008

MATHEMATICA

s=0; lst={s}; Do[s+=n++ +10; AppendTo[lst, s], {n, 0, 6!, 2}]; lst [From Vladimir Joseph Stephan Orlovsky, Nov 17 2008]

CROSSREFS

Sequence in context: A217573 A211482 A177791 * A014367 A063710 A157917

Adjacent sequences:  A028566 A028567 A028568 * A028570 A028571 A028572

KEYWORD

nonn,easy

AUTHOR

Patrick De Geest

STATUS

approved

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Last modified April 21 05:28 EDT 2014. Contains 240824 sequences.