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45-gonal numbers: n*(43*n-41)/2.
1

%I #37 Feb 10 2023 12:02:14

%S 1,45,132,262,435,651,910,1212,1557,1945,2376,2850,3367,3927,4530,

%T 5176,5865,6597,7372,8190,9051,9955,10902,11892,12925,14001,15120,

%U 16282,17487,18735,20026,21360,22737,24157,25620,27126,28675,30267

%N 45-gonal numbers: n*(43*n-41)/2.

%C Similar to 21-gonal and 15-gonal numbers (A051873, A051867).

%H Vincenzo Librandi, <a href="/A098924/b098924.txt">Table of n, a(n) for n = 1..1000</a>

%H <a href="/index/Pol#polygonal_numbers">Index to sequences related to polygonal numbers</a>

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

%F a(n) = n*(43*n-41)/2.

%F G.f.: x*(1+42*x)/(1-x)^3. - _Bruno Berselli_, Feb 04 2011

%F a(n) = 3*a(n-1) -3*a(n-2) +a(n-3). - _Vincenzo Librandi_, Jul 08 2012

%F E.g.f.: exp(x)*(x + 43*x^2/2). - _Nikolaos Pantelidis_, Feb 10 2023

%t Table[n(43n - 41)/2, {n, 1, 40}] (* _Stefan Steinerberger_, Feb 15 2006 *)

%t CoefficientList[Series[(1+42*x)/(1-x)^3,{x,0,50}],x] (* _Vincenzo Librandi_, Jul 08 2012 *)

%t LinearRecurrence[{3,-3,1},{1,45,132},40] (* _Harvey P. Dale_, Jan 24 2015 *)

%o (Magma)[n*(43*n-41)/2: n in [1..50]]; // _Vincenzo Librandi_, Jul 08 2012

%o (PARI) a(n)=n*(43*n-41)/2 \\ _Charles R Greathouse IV_, Oct 16 2015

%Y Cf. A051867, A051873.

%K nonn,easy

%O 1,2

%A _Parthasarathy Nambi_, Oct 18 2004

%E More terms from _Stefan Steinerberger_, Feb 15 2006