



0, 20, 80, 180, 320, 500, 720, 980, 1280, 1620, 2000, 2420, 2880, 3380, 3920, 4500, 5120, 5780, 6480, 7220, 8000, 8820, 9680, 10580, 11520, 12500, 13520, 14580, 15680, 16820, 18000, 19220, 20480, 21780, 23120, 24500, 25920, 27380, 28880, 30420, 32000
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OFFSET

0,2


COMMENTS

Sequence found by reading the line from 0, in the direction 0, 20,..., in the square spiral whose vertices are the generalized dodecagonal numbers A195162. Semiaxis opposite to A195317 in the same spiral.


LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..10000


FORMULA

a(n) = 20*A000290(n) = 10*A001105(n) = 5*A016742(n) = 4*A033429(n) = 2*A033583(n).
a(0)=0, a(1)=20, a(2)=80, a(n)=3*a(n1)3*a(n2)+a(n3).  Harvey P. Dale, Jan 18 2013


MATHEMATICA

20Range[0, 40]^2 (* or *) LinearRecurrence[{3, 3, 1}, {0, 20, 80}, 50] (* Harvey P. Dale, Jan 18 2013 *)


PROG

(MAGMA) [20*n^2:n in [0..40]]; // Vincenzo Librandi, Sep 20 2011


CROSSREFS

Bisection of A195148.
Cf. A033581, A139098, A033583, A135453, A144555, A016802, A195321, A195323.
Sequence in context: A083127 A211613 A002609 * A200424 A211463 A244449
Adjacent sequences: A195319 A195320 A195321 * A195323 A195324 A195325


KEYWORD

nonn,easy


AUTHOR

Omar E. Pol, Sep 16 2011


STATUS

approved



