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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
FORMULA
a(n) = A007978(A000290(n)) = A007978(n^2).
a(n) = A235918(n)+1.
Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = Sum_{k>=0} 1/A019554(A003418(k)) = 2.91240643793540602415... . - Amiram Eldar, Jan 14 2024
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.
Sequence in context: A087242 A123556 A284017 * A053669 A342309 A112047
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jan 26 2014
STATUS
approved

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Last modified June 19 06:35 EDT 2024. Contains 373492 sequences. (Running on oeis4.)