MathDB
Triangular array of numbers and 100th row

Source:

November 21, 2005
modular arithmeticnumber theorygreatest common divisorarithmetic series

Problem Statement

Consider the triangular array of numbers with 0,1,2,3,...0,1,2,3,... along the sides and interior numbers obtained by adding the two adjacent numbers in the previous row. Rows 11 through 66 are shown.
\begin{tabular}{ccccccccccc} & & & & & 0 & & & & & \\ & & & & 1 & & 1 & & & & \\ & & & 2 & & 2 & & 2 & & & \\ & & 3 & & 4 & & 4 & & 3 & & \\ & 4 & & 7 & & 8 & & 7 & & 4 & \\ 5 & & 11 & & 15 & & 15 & & 11 & & 5 \end{tabular}
Let f(n)f(n) denote the sum of the numbers in row nn. What is the remainder when f(100)f(100) is divided by 100100?
<spanclass=latexbold>(A)</span> 12<spanclass=latexbold>(B)</span> 30<spanclass=latexbold>(C)</span> 50<spanclass=latexbold>(D)</span> 62<spanclass=latexbold>(E)</span> 74<span class='latex-bold'>(A)</span>\ 12\qquad <span class='latex-bold'>(B)</span>\ 30 \qquad <span class='latex-bold'>(C)</span>\ 50 \qquad <span class='latex-bold'>(D)</span>\ 62 \qquad <span class='latex-bold'>(E)</span>\ 74