5, 4, 12, 13, 3, 6, 10, 15. 5 + 4 = 9 4 + 12 = 16 12 + 13 = 25 13 + 3 = 16 3 + 6 = 9 6 + 10 = 16 10 + 15 = 25.
Is it possible to write all integer from 1 to 10 in a row in some order such that any two adjacent number add up to a prime number ?
Is it possible to write down 1,2,3..100 in some order (one after an other), such that the sum of any two adjacent numbers is a prime number?
The sequence below contains terms that doesn't have any perfect square factors (except 1). 2, 3, 5, 6, 7, 10, 11, 13, 14, 15...
What is the sum of the square-roots of the terms starting from 2 to the largest two-digit term?
On behalf of Sture Sjöstedt
