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a(n) = 7*n^2 + n.
2

%I #27 Jul 16 2022 07:30:48

%S 0,8,30,66,116,180,258,350,456,576,710,858,1020,1196,1386,1590,1808,

%T 2040,2286,2546,2820,3108,3410,3726,4056,4400,4758,5130,5516,5916,

%U 6330,6758,7200,7656,8126,8610,9108,9620,10146,10686,11240,11808,12390,12986,13596

%N a(n) = 7*n^2 + n.

%C First bisection of A219191. - _Bruno Berselli_, Nov 15 2012

%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).

%F a(n) = A000290(n)*7 + n = A033582(n) + n. - _Omar E. Pol_, Dec 22 2008

%F a(n) = a(n-1) + 14*n - 6 with n>0, a(0)=0. - _Vincenzo Librandi_, Nov 17 2010

%e From _Bruno Berselli_, Oct 27 2017: (Start)

%e After 0:

%e 8 = -(1) + (2+3+4).

%e 30 = -(1+2) + (3+4+5+6+7+8).

%e 66 = -(1+2+3) + (4+5+6+7+8+9+10+11+12).

%e 116 = -(1+2+3+4) + (5+6+7+8+9+10+11+12+13+14+15+16). (End)

%o (PARI) a(n)=7*n^2+n \\ _Charles R Greathouse IV_, Jun 17 2017

%Y Cf. A000290, A033582. - _Omar E. Pol_, Dec 22 2008

%K nonn,easy

%O 0,2

%A Evgeniy A. Chukhlomin (dkea(AT)yandex.ru), Feb 18 2004