MathDB
Digit Sequence

Source:

November 24, 2005
floor function

Problem Statement

Consider the sequence of numbers: 4,7,1,8,9,7,6,…. 4, 7, 1, 8, 9, 7, 6, \ldots . For n>2 n > 2, the n nth term of the sequence is the units digit of the sum of the two previous terms. Let Sn S_n denote the sum of the first n n terms of this sequence. The smallest value of n n for which Sn>10,000 S_n > 10,000 is: <spanclass=′latex−bold′>(A)</span> 1992<spanclass=′latex−bold′>(B)</span> 1999<spanclass=′latex−bold′>(C)</span> 2001<spanclass=′latex−bold′>(D)</span> 2002<spanclass=′latex−bold′>(E)</span> 2004 <span class='latex-bold'>(A)</span>\ 1992 \qquad <span class='latex-bold'>(B)</span>\ 1999 \qquad <span class='latex-bold'>(C)</span>\ 2001 \qquad <span class='latex-bold'>(D)</span>\ 2002 \qquad <span class='latex-bold'>(E)</span>\ 2004
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