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A236454 Smallest number not dividing n^2. 5
2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Differs from A053669, "smallest prime not dividing n", for the first time at n=210, where a(210)=8, while A053669(210)=11. A235921 lists all n for which a(n) differs from A053669(n).

Differs from A214720 at n=2, 210, 630, 1050, 1470, 1890, 2310,.... - R. J. Mathar, Mar 30 2014

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A007978(A000290(n)) = A007978(n^2).

a(n) = A235918(n)+1.

MAPLE

A236454 := proc(n)

    for m from 2 do

        if modp(n^2, m) <> 0 then

            return m;

        end if;

    end do:

end proc:# R. J. Mathar, Mar 30 2014

MATHEMATICA

Join[{2, 3}, Table[Complement[Range[n], Divisors[n^2]][[1]], {n, 3, 90}]] (* Harvey P. Dale, Mar 18 2018 *)

PROG

(Scheme) (define (A236454 n) (A007978 (A000290 n)))

CROSSREFS

One more than A235918.

Cf. also A000290, A007978, A053669, A235921.

Sequence in context: A087242 A123556 A284017 * A053669 A112047 A112048

Adjacent sequences:  A236451 A236452 A236453 * A236455 A236456 A236457

KEYWORD

nonn

AUTHOR

Antti Karttunen, Jan 26 2014

STATUS

approved

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Last modified April 24 10:10 EDT 2019. Contains 322420 sequences. (Running on oeis4.)