

A043885


Numbers k such that 2 and 3 occur juxtaposed in the base4 representation of k but not of k+1.


1



11, 14, 27, 30, 47, 59, 62, 75, 78, 91, 94, 111, 123, 126, 139, 142, 155, 158, 191, 203, 206, 219, 222, 239, 251, 254, 267, 270, 283, 286, 303, 315, 318, 331, 334, 347, 350, 367, 379, 382, 395, 398, 411, 414, 447, 459, 462, 475, 478, 495, 507, 510, 523, 526, 539, 542
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


LINKS



EXAMPLE

27 is in the sequence as 27_10 = 123_4 which has 23 juxtaposed in its base4 representationand 28_10 = 130_4 does not have 23 juxtaposed in its base4 representation.  David A. Corneth, Aug 28 2023


MATHEMATICA

SequencePosition[Table[If[SequenceCount[IntegerDigits[n, 4], {2, 3}]>0  SequenceCount[ IntegerDigits[ n, 4], {3, 2}]>0, 1, 0], {n, 500}], {1, 0}][[;; , 1]] (* Harvey P. Dale, Aug 28 2023 *)


PROG

(PARI) is(n) = {has23juxtaposed(n) && !has23juxtaposed(n+1)}
has23juxtaposed(n) = {my(d = digits(n, 4)); for(i = 1, #d1, if(d[i] == 2 && d[i+1] == 3, return(1)); if(d[i] == 3 && d[i+1] == 2, return(1))); 0} \\ David A. Corneth, Aug 28 2023


CROSSREFS



KEYWORD

nonn,base


AUTHOR



EXTENSIONS



STATUS

approved



