Levine's sequence is the integer sequence formed by the final terms of recursively constructed rows. Start with the row . If a row is
, the next row contains
copies of 1, followed by
copies of 2, continuing through
copies of
(Sloane 1999, Numberphile 2021). Thus the first three rows
are
,
, and
, and the first terms of Levine's sequence are 1, 2,
2, 3, 4, 7, 14, 42, 213, 2837, 175450, ... (OEIS A011784).
If
is the last term in row
, then
is the number of elements in row
. The number of elements in row
is the sum of the elements in row
, so
is that row sum (Sloane 1999).