

A153780


10 times pentagonal numbers: 5n(3n1).


0



0, 10, 50, 120, 220, 350, 510, 700, 920, 1170, 1450, 1760, 2100, 2470, 2870, 3300, 3760, 4250, 4770, 5320, 5900, 6510, 7150, 7820, 8520, 9250, 10010, 10800, 11620, 12470, 13350, 14260, 15200, 16170, 17170, 18200, 19260, 20350
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OFFSET

0,2


LINKS

Table of n, a(n) for n=0..37.


FORMULA

a(n) = 15n^2  5n = A000326(n)*10 = A049450(n)*5 = A152734(n)*2.
a(n)=30*n+a(n1)20 (with a(0)=0). [From Vincenzo Librandi, Aug 03 2010]
G.f.: 10*x*(1+2*x)/(1x)^3. [Colin Barker, Feb 14 2012]


EXAMPLE

a(1)=30*1+020=10; a(2)=30*2+1020=50; a(3)=30*3+5020=120 [From Vincenzo Librandi, Aug 03 2010]


CROSSREFS

Cf. A000326, A049450, A152734, A152996, A153449.
Sequence in context: A036786 A085444 A102915 * A196507 A008531 A051230
Adjacent sequences: A153777 A153778 A153779 * A153781 A153782 A153783


KEYWORD

easy,nonn


AUTHOR

Omar E. Pol, Jan 01 2009


STATUS

approved



