OFFSET
0,2
COMMENTS
The digital roots of the terms are (1, 2, 4, 8, 7, 5) with cyclic repetitions.
Initial values 2, 4, 5, 7 or 8 yield the same repeating pattern; for initial values 3 or 6 the repeating pattern is (3, 6), and for a(0) = 9 it is 9.
LINKS
Eric Angelini, Fun with roots, personal blog CinquanteSignes.blogspot.com (and post to the SeqFan list), Jul 28 2024.
FORMULA
a(6n) = a(6n-6)*10^6 + 124875.
EXAMPLE
The digital root of a(0) = 1 is 1, thus a(1) = 11.
Then, the digital root of a(1) = 11 is 2, thus a(2) = 112, etc.
PROG
(PARI) A375101_upto(N, a=1)=vector(N, i, a+=if(i>1, 9*a+(a-1)%9+1))
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
M. F. Hasler, Jul 30 2024
STATUS
approved