|
In recreational mathematics, a Keith number or repfigit number (short for repetitive Fibonacci-like digit) is a number in the following integer sequence: :14, 19, 28, 47, 61, 75, 197, 742, 1104, 1537, 2208, 2580, .... Keith numbers were introduced by Mike Keith in 1987. They are computationally very challenging to find, with only about 100 known. ==Introduction== To determine whether an ''n''-digit number ''N'' is a Keith number, create a Fibonacci-like sequence that starts with the ''n'' decimal digits of ''N'', putting the most significant digit first. Then continue the sequence, where each subsequent term is the sum of the previous ''n'' terms. By definition, ''N'' is a Keith number if ''N'' appears in the sequence thus constructed. As an example, consider the 3-digit number ''N'' = 197. The sequence goes like this: :1, 9, 7, 17, 33, 57, 107, 197, 361, ... Because 197 appears in the sequence, 197 is seen to be indeed a Keith number. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Keith number」の詳細全文を読む スポンサード リンク
|