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A117213 a(n) = smallest term of sequence A002110 divisible by n-th squarefree positive integer. 2
1, 2, 6, 30, 6, 210, 30, 2310, 30030, 210, 30, 510510, 9699690, 210, 2310, 223092870, 30030, 6469693230, 30, 200560490130, 2310, 510510, 210, 7420738134810, 9699690, 30030, 304250263527210, 210, 13082761331670030, 223092870 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..1441

FORMULA

For n >= 2, a(n) = product of the primes <= A073482(n).

EXAMPLE

10 is the 7th squarefree integer. And 2*3*5 = 30 is the smallest primorial number divisible by 10 = 2*5. So a(7) = 30.

MAPLE

issquarefree := proc(n::integer) local nf, ifa, lar ; nf := op(2, ifactors(n)) ; for ifa from 1 to nops(nf) do lar := op(1, op(ifa, nf)) ; if op(2, op(ifa, nf)) >= 2 then RETURN(0) ; fi ; od : RETURN(lar) ; end: primor := proc(n::integer) local resul, nepr ; resul :=2 ; nepr :=3 ; while nepr <= n do resul := resul*nepr ; nepr:=nextprime(nepr) ; od : RETURN(resul) ; end: printf("1, ") ; for n from 2 to 100 do lfa := issquarefree(n) ; if lfa > 0 then printf("%a, ", primor(lfa) ) ; fi ; od : # R. J. Mathar, Apr 02 2006

MATHEMATICA

Select[Array[Which[# == 1, 1, SquareFreeQ@ #, Product[Prime@ i, {i, PrimePi@ FactorInteger[#][[-1, 1]]}], True, 0] &, 50], # > 0 & ] (* Michael De Vlieger, Sep 30 2017 *)

CROSSREFS

Cf. A002110, A073482, A117214.

Sequence in context: A074168 A079615 A076978 * A127797 A338441 A077634

Adjacent sequences:  A117210 A117211 A117212 * A117214 A117215 A117216

KEYWORD

nonn

AUTHOR

Leroy Quet, Mar 03 2006

EXTENSIONS

More terms from R. J. Mathar, Apr 02 2006

STATUS

approved

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Last modified June 18 06:02 EDT 2021. Contains 345098 sequences. (Running on oeis4.)