發送短信 : On the operator bk related to the bessel heat equation

  ______    ______   _____      ______    ____    
 /_   _//  /_   _// |  __ \\   /_   _//  |  _ \\  
 `-| |,-    -| ||-  | |  \ ||   -| ||-   | |_| || 
   | ||     _| ||_  | |__/ ||   _| ||_   | .  //  
   |_||    /_____// |_____//   /_____//  |_|\_\\  
   `-`'    `-----`   -----`    `-----`   `-` --`