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Self-convolution of natural numbers >= 3.
2

%I #23 Sep 08 2022 08:44:47

%S 9,24,46,76,115,164,224,296,381,480,594,724,871,1036,1220,1424,1649,

%T 1896,2166,2460,2779,3124,3496,3896,4325,4784,5274,5796,6351,6940,

%U 7564,8224,8921,9656,10430,11244,12099,12996,13936,14920,15949

%N Self-convolution of natural numbers >= 3.

%H Vincenzo Librandi, <a href="/A023551/b023551.txt">Table of n, a(n) for n = 1..10000</a>

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-6,4,-1).

%F a(n) = n*(n^2 + 15*n + 38)/6. - Robert Lester (RobertLester(AT)Earthlink.net), Jan 31 2005

%F G.f.: x*(3-2*x)^2/(1-x)^4. - _Bruno Berselli_, Oct 21 2011

%o (PARI) a(n) = n*(n^2+15*n+38)/6 \\ _Charles R Greathouse IV_, Oct 21 2011

%o (Magma) [n*(n^2+15*n+38)/6: n in [1..50]]; // _Vincenzo Librandi_, Oct 22 2011

%K nonn,easy

%O 1,1

%A _Clark Kimberling_