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A196272 Number of occurrences of '11' in base-4 expansion of n. 1
0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,22

COMMENTS

This is to base 4 A007090 as A196096 is to base 3 and A007089 as A014081 is to base 2 A007088.

Records occur at places where n ='111...11' in base b, that is n = (b^(k+1)-1)/(b-1) for some k > 0, in particular for b=4 as listed in A002450(k+1). - R. J. Mathar, Sep 30 2011

LINKS

T. D. Noe, Table of n, a(n) for n = 0..1000

EXAMPLE

a(21) = 2 because 21 (base 10) = 111 (base 4), whose first two digits are one, and whose rightmost two digits are the second substring of "11".

MAPLE

A196272 := proc(n)

        local a, dgs ;

        a := 0 ;

        dgs := convert(n, base, 4) ;

        for i from 1 to nops(dgs)-1 do

                if op(i, dgs)=1 and op(i+1, dgs)=1 then

                        a := a+1 ;

                end if;

        end do;

        a ;

end proc:

seq(A196272(n), n=0..100) ; # R. J. Mathar, Sep 30 2011

MATHEMATICA

Table[d = IntegerDigits[n, 4]; Count[Partition[d, 2, 1], {1, 1}], {n, 0, 100}] (* T. D. Noe, Sep 30 2011 *)

CROSSREFS

Cf. A007090, A014081, A196096.

Sequence in context: A108511 A261160 A270668 * A086073 A053622 A016408

Adjacent sequences:  A196269 A196270 A196271 * A196273 A196274 A196275

KEYWORD

nonn,easy,base

AUTHOR

Jonathan Vos Post, Sep 29 2011

STATUS

approved

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Last modified June 19 11:23 EDT 2019. Contains 324219 sequences. (Running on oeis4.)