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%I #8 Jun 17 2017 03:55:05
%S 0,1,15,105,465,1540,4186,9870,20910,40755,74305,128271,211575,335790,
%T 515620,769420,1119756,1594005,2224995,3051685,4119885,5483016,
%U 7202910,9350650,12007450,15265575,19229301,24015915,29756755,36598290
%N Triangular numbers with square pyramidal indices.
%H <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (7,-21,35,-35,21,-7,1).
%F let SP(m) be the m-th square pyramidal number m*(m+1)*(2*m+1)/6 and T(k) be the k-th Triangular number k*(k+1)/2 then a(n)=T(SP(n)).
%F G.f.: x*(1+8*x+21*x^2+10*x^3)/(1-x)^7. [_Colin Barker_, Apr 30 2012]
%e SP(3)=14 -> a(3)=T(SP(3))=T(14)=105; SP(4)=30 -> a(4)=T(SP(4))=T(30)=465 etc
%Y Cf. A077538.
%K easy,nonn
%O 0,3
%A Bruce Corrigan (scentman(AT)myfamily.com), Nov 14 2002
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