The Twelve Days of Christmas and A003990, A002620, etc.

[Alonso Del Arte]

As furniture stores gear up to celebrate Christmas in July, I was
thinking about the gift totals in the song "The Twelve Days of
Christmas."

On the first day, you have one partridge in a pear tree. On the second
day, you have two partridges in pear trees and two turtle doves. By
the twelfth day, you have 12 partridges in pear trees, 22 turtle
doves, 30 French hens, 36 calling birds, 40 golden rings, 42 geese
a-laying, 42 swans a-swimming, 40 maids a-milking, 36 ladies dancing,
30 lords a-leaping, 22 pipers piping and 12 drummers drumming. I
expected to find this sequence in the OEIS, but I wasn't expecting
five results, none of which mention this famous song. I'm not sure
under which one it would be appropriate to file the comment.

I also looked up 1, 2, 4, 6, 9, 12, 16, 20, 25, 30, 36, 42, the
largest number of a distinct gift you'd have on the n-th day. This
yielded seven results, and extending the sequence to n = 15 (I have no
idea what the extra gifts would be) still gives five results.

Alonso