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2011 BAMO 7 Pascal Triange a,b,c,d with b=2a and d=2c

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August 27, 2019
Pascal's TrianglecombinatoricsSum

Problem Statement

Does there exist a row of Pascal’s Triangle containing four distinct values a,b,ca,b,c and dd such that b=2ab = 2a and d=2cd = 2c? Recall that Pascal’s triangle is the pattern of numbers that begins as follows https://cdn.artofproblemsolving.com/attachments/2/1/050e56f0f1f1b2a9c78481f03acd65de50c45b.png where the elements of each row are the sums of pairs of adjacent elements of the prior row. For example, 10=4+610 =4+6. Also note that the last row displayed above contains the four elements a=5,b=10,d=10,c=5a = 5,b = 10,d = 10,c = 5, satisfying b=2ab = 2a and d=2cd = 2c, but these four values are NOT distinct.