why did snape call himself the half blood prince
Severus Snape Before leaving Hogwarts to accompany Dumbledore in locating another horcrux –part of Voldemort's soul– Harry discovers from Professor Trelawney that it was Snape who overheard the prophecy and told it to Voldemort, resulting in Voldemort hunting down Harry and his parents. Despite this and Harry's angry questions, Dumbledore avers his trust in Snape. Returning to Hogwarts after retrieving Voldemort's Horcrux, Harry and Dumbledore alight atop the school's astronomy tower. Gravely weakened by the horcrux's protective potion, Dumbledore tells Harry he must fetch Snape, but before Harry can leave, Draco suddenly arrives, intending to carry out Voldemort's order to assassinate Dumbledore, closely followed by other Death Eaters (followers of Voldemort), and Snape. Snape interrupts the planned murder, killing the headmaster himself.[36] Harry, who is paralysed under his invisibility cloak by Dumbledore for his own protection, witnesses the kill, and is released upon Dumbledore's death. Enraged, he pursues Snape, Draco, and the Death Eaters as they flee the castle. Snape easily blocks Harry's spells and jeeringly points out Harry's mistakes, but never strikes back. During the confrontation, Snape reveals himself as the eponymous "Half-Blood Prince" (being the half-blood son of Muggle Tobias Snape and pure-blood Eileen Prince). Snape passes through the school gates and Disapparates with Draco in tow at the book's end.[37] The full relationship between Dumbledore and Snape and the reason for Snape's actions remain unknown until the final book. In an interview, Rowling mentioned that at this point in the series, the Harry–Snape relationship has become "as personal, if not more so, than Harry–Voldemort."[38]
Harry Potter and the Half-Blood Prince (film) Lord Voldemort is tightening his grip on both the wizarding and Muggle worlds, kidnapping Ollivander from Diagon Alley and destroying the Millennium Bridge. After the Malfoy family is disgraced when Lucius is apprehended and sent to Azkaban for his involvement with the Death Eaters, Voldemort chooses Draco to carry out a secret mission at Hogwarts. Bellatrix Lestrange and Narcissa Malfoy, Draco's mother, seek help from Severus Snape, who claims to have been acting as a mole within the Order of the Phoenix all along. Snape makes an Unbreakable Vow with Narcissa to protect Draco and fulfill the assignment if he fails.
Marcus Álvarez
1 + 2 + 3 + 4 + ⋯ which increases without bound as n goes to infinity. Because the sequence of partial sums fails to converge to a finite limit, the series does not have a sum.