OFFSET
1,1
COMMENTS
Positions of 4 in A277543. Numbers that have 4 as their rightmost nonzero digit when written in base 5.
This is one sequence in a 4-way splitting of the positive integers; the other three are indicated in the Mathematica program. All these sequences have the same density of 1/4.
Is there some n with a 3 or a 4 in base 5 such that a(n) = 4n + 1? - David A. Corneth, Oct 23 2016
LINKS
Clark Kimberling, Table of n, a(n) for n = 1..10000
FORMULA
Conjecture: a(n) = 4*n if and only if n is in A033042. - David A. Corneth, Oct 23 2016
MATHEMATICA
PROG
(PARI) isok(n) = n/5^valuation(n, 5) % 5 == 4; \\ Michel Marcus, Oct 21 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Oct 20 2016
STATUS
approved