A number n is said to be economical if the prime power factori-sation of n can be written with no more digits than n itself. We show that under a plausible hypothesis, related to the twin prime conjecture, there are arbitrarily long sequences of consecutive economial numbers, and exhibit such a sequence of length 9.

Nowadays in the light of technological, economical and social changes, the problems of overall occupation of people and continuous growth of economy become more important and complex. Continuous development of people’s knowledge and skills, investment in education and vocational training are the main factors stimulating the economical and social development of the state. This paper analysis the...

in this study tried to calculate attributed-based index and measurement of farmer’s attention to wheat (triticum aestivum l.) seed environmental, cropping and marketing attribute and evaluate social– economical factors influencing on this index. after this estimation, effective factors have selected. related data to 102 mashhad wheat producers, iran were used for estimations poisson regression....