OFFSET
1,2
COMMENTS
Numbers with 1's are excluded.
Numbers written with digits 0,6,8,9, with 6 and 9 interchanged when reversed. - Robert Israel, Jul 02 2018
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
MAPLE
f:= proc(n) local L, Lp, nl;
L:= subs(1=6, 2=8, 3=9, convert(n, base, 4));
nl:= nops(L);
Lp:= subs([6=9, 9=6], L);
add(Lp[-i]*10^(i-1), i=1..nl)+add(L[i]*10^(nl+i-1), i=1..nl);
end proc:
g:= proc(n) local L, Lp, nl;
L:= subs(1=6, 2=8, 3=9, convert(n, base, 4));
nl:= nops(L);
Lp:= subs([6=9, 9=6], L);
seq(add(Lp[-i]*10^(i-1), i=1..nl)+x*10^nl+add(L[i]*10^(nl+i), i=1..nl), x=[0, 8]);
end proc:
0, 8, seq(op([seq(f(n), n=4^i..4^(i+1)-1), seq(g(n), n=4^i..4^(i+1)-1)]), i=0..2); # Robert Israel, Jul 02 2018
MATHEMATICA
Select[Range[0, 600010], ContainsOnly[IntegerDigits[#], {0, 6, 8, 9}]&&IntegerReverse[FromDigits[IntegerDigits[#]/.{6->9, 9->6}]]==#&] (* James C. McMahon, Apr 30 2024 *)
PROG
(Haskell) main=print$"0":concat[concat[[reverse(reverse(map f x)++z++x)|x<-y]|z<-["", "0"]]|y<-s(iterate i"6")]; f '0'='0'; f '6'='9'; f '8'='8'; f '9'='6'; i('0':x)='6':x; i('6':x)='8':x; i('8':x)='9':x; i('9':x)='0':i x; i""="6"; s(x:y@(z:_))=let w:v=s y in if length x==length z then(x:w):v else[x]:w:v
(Python)
from itertools import count, islice, product
def ud(s): return s[::-1].translate({ord('6'):ord('9'), ord('9'):ord('6')})
def agen():
yield from [0, 8]
for d in count(2):
for start in "689":
for rest in product("0689", repeat=d//2-1):
left = start + "".join(rest)
right = ud(left)
for mid in [[""], ["0", "8"]][d%2]:
yield int(left + mid + right)
print(list(islice(agen(), 48))) # Michael S. Branicky, Mar 29 2022
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Paul Stoeber (pstoeber(AT)uni-potsdam.de), Oct 09 2005
EXTENSIONS
Corrected by Robert Israel, Jul 02 2018
STATUS
approved