

A022268


a(n) = n*(11*n  1)/2.


14



0, 5, 21, 48, 86, 135, 195, 266, 348, 441, 545, 660, 786, 923, 1071, 1230, 1400, 1581, 1773, 1976, 2190, 2415, 2651, 2898, 3156, 3425, 3705, 3996, 4298, 4611, 4935, 5270, 5616, 5973, 6341, 6720, 7110, 7511, 7923, 8346, 8780, 9225, 9681, 10148, 10626, 11115
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OFFSET

0,2


COMMENTS

Number of sets with two elements that can be obtained by selecting distinct elements from two sets with 2n and 3n elements respectively and n common elements.  Polina S. Dolmatova (polinasport(AT)mail.ru), Jul 11 2003


LINKS

G. C. Greubel, Table of n, a(n) for n = 0..5000
Index entries for linear recurrences with constant coefficients, signature (3,3,1).


FORMULA

G.f.: x*(5 + 6*x)/(1x)^3.  Bruno Berselli, Feb 11 2011
a(n) = 11*n + a(n1)  6 for n>0.  Vincenzo Librandi, Aug 04 2010
a(n) = A000217(6*n1)  A000217(5*n1).  Bruno Berselli, Oct 17 2016
From Wesley Ivan Hurt, Dec 04 2016: (Start)
a(n) = 3*a(n1)  3*a(n2) + a(n3) for n > 2.
a(n) = (1/9) * Sum_{i=n..10n1} i. (End)
E.g.f.: (1/2)*(11*x^2 + 10*x)*exp(x).  G. C. Greubel, Jul 17 2017


MAPLE

A022268:=n>n*(11*n  1)/2: seq(A022268(n), n=0..50); # Wesley Ivan Hurt, Dec 04 2016


MATHEMATICA

Table[n (11 n  1)/2, {n, 0, 40}] (* Bruno Berselli, Oct 14 2016 *)


PROG

(PARI) a(n)=n*(11*n1)/2 \\ Charles R Greathouse IV, Sep 24 2015
(MAGMA) [n*(11*n  1)/2 : n in [0..50]]; // Wesley Ivan Hurt, Dec 04 2016


CROSSREFS

Cf. A000217, A022281.
Cf. index to sequence with numbers of the form n*(d*n+10d)/2 in A140090.
Cf. similar sequences listed in A022288.
Sequence in context: A146846 A296200 A041825 * A201279 A146721 A099979
Adjacent sequences: A022265 A022266 A022267 * A022269 A022270 A022271


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane


STATUS

approved



