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例子
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例如:A(x)=1+x+4*x^2/2!+18*x^3/3!+100*x^4/4!+660*x^5/5!+5038*x^6/6!+43624*x^7/7!+422252*x^8/8!+4516380*x^9/9!+52885644*x ^10/10!+。。。
Product_{k=1..n}(1+k*y+y^2)中的系数,n>=0,形成三角形A249790型:
[1];
[1, 1, 1];
[1, 3, 4, 3, 1];
[1, 6, 14, 18, 14, 6, 1];
[1, 10, 39, 80, 100, 80, 39, 10, 1];
[1, 15, 90, 285, 539, 660, 539, 285, 90, 15, 1];
[1,211181840,2339,4179,5038,4179,2339,840,181,21,1];
[1, 28, 329, 2128, 8400, 21392, 36630, 43624, 36630, 21392, 8400, 2128, 329, 28, 1]; ...
其中行的中心项构成此序列。
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