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a(n)=A033003(n)/6.
1

%I #8 Feb 03 2014 12:33:46

%S 1,2,3,4,25,27,28,29,50,51,53,54,75,76,77,79,100,101,102,103,626,627,

%T 628,629,675,676,678,679,700,701,702,704,725,726,727,728,1251,1252,

%U 1253,1254,1275,1277,1278,1279,1325,1326,1327,1329

%N a(n)=A033003(n)/6.

%C Also: Numbers which, written in base 25, have all digits less than 5 and no two adjacent digits equal. - _M. F. Hasler_, Feb 03 2014

%o (PARI) is_A043309(n)=(n=[n])&&!until(!n[1],((n=divrem(n[1],25))[2]<5 && n[1]%5!=n[2])||return) \\ _M. F. Hasler_, Feb 03 2014

%Y Cf. A043307 - A043320, A043291, A033001 - A033014, A033016 - A033029.

%K nonn,base

%O 1,2

%A _Clark Kimberling_