My Math Forum Stretched numbers : closed formula

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 September 26th, 2016, 06:06 PM #1 Banned Camp   Joined: Dec 2013 Posts: 1,117 Thanks: 41 Stretched numbers : closed formula Hi, Each time I post something controversial or insulting you are in hurry to answer. But when it comes to mathematics you become silent like fishes under the sea. I have seen very interesting post in french here : Enigme Nombres serrĂ©s @ Prise2Tete He defines (Nodgim is his nickname) les nombres serres (stretched numbers) as the composite numbers a*b where b<=2a and b>=a 2=1*2, 6=2*3,9=3*3, 20=4*5 etc...are all stretched numbers. 1. Can you find all the stretched numbers less or equal to 10.000? 2. Someone gave on the same thread a formula not correct can you find a closed formula for those numbers? 3. Can you find a formula for counting all the composite numbers but the stretched numbers? 4. If you find a closed formula for both kind of composite numbers you will have the first closed formula counting exactly the prime numbers. Anyone interested could contribute. Now I promise that I will never put my feet here because I know that no one here is really interested in mathematics. You have big big big problem with yourselves. My advise : do other things than mathematics (art, business, etc...). FORGET ABOUT MATHS YOU ARE NOT INTERESTED AT ALL BY MATHEMATICS. GOOD BYE AND GOOD LUCK! I CUT OFF INTERNET ONCE FOR ALL. Thanks from Joppy

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