<P> Fibonacci became a guest of Emperor Frederick II, who enjoyed mathematics and science . In 1240, the Republic of Pisa honored Fibonacci (referred to as Leonardo Bigollo) by granting him a salary in a decree that recognized him for the services that he had given to the city as an advisor on matters of accounting and instruction to citizens . </P> <P> The date of Fibonacci's death is not known, but it has been estimated to be between 1240 and 1250, most likely in Pisa . </P> <P> In the Liber Abaci (1202), Fibonacci introduced the so - called modus Indorum (method of the Indians), today known as the Hindu--Arabic numeral system . The book advocated numeration with the digits 0--9 and place value . The book showed the practical use and value of the new Hindu - Arabic numeral system by applying the numerals to commercial bookkeeping, converting weights and measures, calculation of interest, money - changing, and other applications . The book was well - received throughout educated Europe and had a profound impact on European thought . No copies of the 1202 edition are known to exist . </P> <P> The 1228 edition, first section introduces the Hindu - Arabic numeral system and compares the system with other systems, such as Roman numerals, and methods to convert the other numeral systems into Hindu - Arabic numerals . Replacing the Roman numeral system, its ancient Egyptian multiplication method, and using an abacus for calculations, with a Hindu - Arabic numeral system was an advance in making business calculations easier and faster, which led to the growth of banking and accounting in Europe . </P>

Who is the fibonacci sequence named after and what is the name of the book he wrote