OFFSET
0,2
COMMENTS
This sequence is bounded as the decimal representation of any term in A336668 is fully determined by at most 9 of its leading digits.
LINKS
Rémy Sigrist, Table of n, a(n) for n = 0..10000
Rémy Sigrist, PARI program for A336669
FORMULA
a(n) = 9 iff n is 11-rough (A008364).
a(k*n) >= a(n) for any n >= 0 and k > 0.
Apparently, when n > 0, a(n) = a(gcd(n, 2^3 * 3^2 * 5 * 7)).
EXAMPLE
For n = 2:
- let m be a two-digit term of A336668 (10 <= m <= 99),
- if m starts with an odd digit, say d = 1, 3, 5, 7 or 9, then m ends with d,
- if m starts with an even digit, say d = 2, 4, 6 or 8, then m ends with any even digit, say t = 0, 2, 4, 6 or 8,
- so a(2) = 5 + 4*5 = 25.
PROG
(PARI) See Links section.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Rémy Sigrist, Jul 29 2020
STATUS
approved