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%I #12 Sep 08 2022 08:45:07
%S 1,103,1130,6070,22355,64981,160468,351660,703365,1308835,2297086,
%T 3841058,6166615,9562385,14390440,21097816,30228873,42438495,58506130,
%U 79350670,106046171,139838413,182162300,234660100,299200525,377898651,473136678,587585530,724227295
%N Sum of squares of numbers that can be written as t*n + u*(n+1) for nonnegative integers t,u in exactly one way.
%D Fred. Schuh, Vragen betreffende een onbepaalde vergelijking, Nieuw Tijdschrift voor Wiskunde, 52 (1964-1965) 193-198.
%H Vincenzo Librandi, <a href="/A076460/b076460.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = n*(n+1)*(7*n^4+2*n^3-6*n^2-n+1)/6.
%F G.f.: x*(1+96*x+430*x^2+288*x^3+25*x^4)/(1-x)^7.
%p seq(1/6*n*(n+1)*(7*n^4+2*n^3-6*n^2-n+1),n=1..30);
%t CoefficientList[Series[(1 + 96 x + 430 x^2 + 288 x^3 + 25 x^4)/(1 - x)^7, {x, 0, 50}], x] (* _Vincenzo Librandi_, Dec 30 2013 *)
%o (Magma) [n*(n+1)*(7*n^4+2*n^3-6*n^2-n+1)/6: n in [1..50]]; // _Vincenzo Librandi_, Dec 30 2013
%Y Cf. A076389, A076461-A076465.
%K easy,nonn
%O 1,2
%A _Floor van Lamoen_, Oct 13 2002
%E More terms from _Vincenzo Librandi_, Dec 30 2013
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