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A180232 n*(17*n-13)/2. 3
0, 2, 21, 57, 110, 180, 267, 371, 492, 630, 785, 957, 1146, 1352, 1575, 1815, 2072, 2346, 2637, 2945, 3270, 3612, 3971, 4347, 4740, 5150, 5577, 6021, 6482, 6960, 7455, 7967, 8496, 9042, 9605, 10185, 10782, 11396, 12027, 12675, 13340, 14022, 14721, 15437, 16170 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

FORMULA

a(n) = n+A051871(n). a(n) = 3*a(n-1)-3*a(n-2)+a(n-3). G.f.: x*(2+15*x) / (1-x)^3.

MATHEMATICA

Table[(n(17n-13))/2, {n, 0, 50}] (* or *) LinearRecurrence[{3, -3, 1}, {0, 2, 21}, 50] (* Harvey P. Dale, Sep 14 2011 *)

PROG

(PARI) a(n)=1/2*(17*n^2 - 13*n);

(MAGMA) [n*(17*n-13)/2:n in [0..40]]; // Vincenzo Librandi, Sep 15 2011

CROSSREFS

Cf. A051871.

Cf. A226488. [Bruno Berselli, Jun 10 2013]

Sequence in context: A074875 A231807 A097718 * A075681 A212257 A034520

Adjacent sequences:  A180229 A180230 A180231 * A180233 A180234 A180235

KEYWORD

nonn,easy

AUTHOR

Graziano Aglietti (mg5055(AT)mclink.it), Aug 18 2010

EXTENSIONS

More terms and g.f. from R. J. Mathar, Aug 29 2010

STATUS

approved

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Last modified November 20 12:30 EST 2017. Contains 294971 sequences.