cp's OEIS Frontend

In November 1987, an editor at the Astrophysical Journal wrote to N. J. A. Sloane with three sequences whose explanation was not known to her. She said: "As to the pedigree of these sequences, not much is known. But they are US in origin, and /not/ Hungarian". One of the three was the number-theoretical sequence A007468. The other two are now A199714 and A199715.

Looking at the first differences (9, 14, 7, 5, 14, 9, 15, 21), one may notice that the last three terms are 3*(3, 5, 7), and the relation 9 = 14 - 5 seems to appear twice. Taking the second differences yields (5, -7, -2, 9, -5, 6, 6), where similar relations 5 - 7 = -2 and 7 + 2 = 9 can be seen. - M. F. Hasler, Mar 14 2018

This puzzle occurs on a trial test by Ron Hoeflin for his Titan Test. It is question 13 on Trial Test F. Link is below. The sequence differences are the alphabetical positions (a is 1, b is 2, etc.) of the letters in the word "ingenious." Since s is 19, the next term is 94 + 19 = 113. Then the sequence ends. - Chris Cole, Mar 03 2023