A043900 - OEIS

%I #25 Aug 25 2021 04:54:40

%S 30,41,66,77,102,113,138,149,174,185,210,221,251,257,282,293,318,329,

%T 354,365,390,401,426,437,467,473,498,509,534,545,570,581,606,617,642,

%U 653,683,689,714,725,750,761,786,797,822,833

%N Numbers k such that 0 and 5 occur juxtaposed in the base-6 representation of k but not of k+1.

%e 30(10) = 50(6) but 31(10) = 51(6), so 30 is in the sequence.

%t Transpose[SequencePosition[Table[If[SequenceCount[IntegerDigits[n,6],{0,5}]>0||SequenceCount[IntegerDigits[n,6],{5,0}]>0,1,0],{n,1000}],{1,0}]][[1]] (* The program uses the SequencePosition and SequenceCount functions from Mathematica version 10 *) (* _Harvey P. Dale_, Jan 14 2016 *)

%o (Sage)

%o @cached_function

%o def str_base6(x):

%o     return ''.join(str(y) for y in x.digits(base=6))

%o [x for x in [1..2000] if '50' in str_base6(x) or '05' in str_base6(x) and not('50' in str_base6(x + 1) or '05' in str_base6(x + 1))]

%o # _Tom Edgar_, May 13 2014

%Y Cf. A007092.

%K nonn,base

%O 1,1

%A _Clark Kimberling_, Dec 11 1999