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A033032
Numbers all of whose base 6 digits are odd.
3
1, 3, 5, 7, 9, 11, 19, 21, 23, 31, 33, 35, 43, 45, 47, 55, 57, 59, 67, 69, 71, 115, 117, 119, 127, 129, 131, 139, 141, 143, 187, 189, 191, 199, 201, 203, 211, 213, 215, 259, 261, 263, 271, 273, 275, 283, 285, 287, 331, 333, 335, 343
OFFSET
1,2
LINKS
FORMULA
If (3^d-1)/2 <= n < (3^(d+1)-1)/2, then a(n+3^d) = a(n) + 6^n, a(n+2*3^d) = a(n) + 2*6^n, and a(n+3^(d+1)) = a(n) + 5*6^n. - Robert Israel, Aug 16 2018
MAPLE
g:= proc(t, d) local L;
L:= convert(3^d+t, base, 3);
add((2*L[i]+1)*6^(i-1), i=1..d);
end proc:
seq(seq(g(t, d), t=0..3^d-1), d=1..4); # Robert Israel, Aug 16 2018
MATHEMATICA
Table[FromDigits[#, 6]&/@Tuples[{1, 3, 5}, n], {n, 4}]//Flatten (* Harvey P. Dale, Dec 24 2022 *)
PROG
(PARI) isok(n) = (n) && (#select(x->((x%2)==0), digits(n, 6)) == 0); \\ Michel Marcus, Aug 17 2018
CROSSREFS
Sequence in context: A152484 A071643 A039578 * A103148 A211138 A178995
KEYWORD
nonn,base
STATUS
approved