OFFSET
0,7
COMMENTS
LINKS
Antti Karttunen, Table of n, a(n) for n = 0..10080
FORMULA
EXAMPLE
From 11 sprouts the following finite side-tree of "factorial beanstalk":
18 19
\ /
14 15
\ /
11
Its leaves are the numbers 14, 18 and 19 (which all occur in A219658), whose factorial base representations (see A007623) are '210', '300' and '301' respectively. The corresponding parent nodes are obtained by subtracting the sum of factorial base digits, thus we get 18-3 = 15 and also 19-4 = 15, thus 15 ('211' in factorial base) is the parent of 18 and 19. For 14 and 15 we get 14-3 = 15-4 = 11, thus 11 is the parent of both 14 and 15, and the common ancestor of all numbers 11, 14, 15, 18 and 19.
For numbers not occurring in A219666 this sequence gives the number of leaves in such subtrees. Thus a(11)=3, a(14)=1 (counting just the leaf 14 itself), a(15)=2 and a(18) = a(19) = 1.
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Nov 10 2013
STATUS
approved