A few weeks ago I was working through the Google Foobar challenges and came upon a problem where I had to calculate a certain function. I could calculate the f

A few weeks ago I was working through the Google Foobar challenges and came upon a problem where I had to calculate a certain function. I could calculate the first few values of the function by hand, but was having trouble coming up with a general expression so I plugged the sequence into OEIS. I was pleasantly surprised to find that not only did OEIS have it, but it was actually the very first sequence in there! (Confusingly it is numbered A000435, not A000001.) OEIS gave me the general expression and from there I could solve the problem!