ERJ Brainteaser – June

This month’s ERJ Brainteaser challenged readers with a numerical sequence puzzle: 3, 11, 19, 37, 55,?. The solution, as correctly identified by multiple participants, is 87. The sequence maps to the atomic numbers of Group 1 elements in the periodic table—alkali metals—specifically: Lithium (3), Sodium (11), Potassium (19), Rubidium (37), Cesium (55), and Francium (87). The French-language framing of the question (“Complétez la liste”) and the later clues (Metal, Group) reinforced the periodic table connection. The correct answer was confirmed by Andrew Knox, Amparo Botella, John Bowen, Kamila Staszewska, Dr Kate Burns, Bharat B Sharma, and Hans-Bernd Luechtefeld, among others. The next teaser will drop on Monday, with solutions and the next challenge following on 22 June due to staff holidays. A separate countdown conundrum (207.65, 100.91, 43.03, 19.30, _? _) was postponed after a technical issue and will resume next week with additional clues (Cu/Sn, Ag, Au).