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A073485 Product of any number of consecutive primes; squarefree numbers with no gaps in their prime factorization. 20
1, 2, 3, 5, 6, 7, 11, 13, 15, 17, 19, 23, 29, 30, 31, 35, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 77, 79, 83, 89, 97, 101, 103, 105, 107, 109, 113, 127, 131, 137, 139, 143, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 210, 211, 221, 223, 227, 229, 233 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A073484(a(n)) = 0 and A073483(a(n)) = 1;

See A097889 for composite terms. - Reinhard Zumkeller, Mar 30 2010

A169829 is a subsequence. - Reinhard Zumkeller, May 31 2010

a(A192280(n)) = 1: complement of A193166.

Also fixed points of A053590: a(n) = A053590(a(n)). - Reinhard Zumkeller, May 28 2012

The Heinz numbers of the partitions into distinct consecutive integers. The Heinz number of a partition p = [p_1, p_2, ..., p_r] is defined as Product(p_j-th prime, j=1...r) (concept used by Alois P. Heinz in A215366 as an "encoding" of a partition). Example: (i) 15 (= 3*5) is in the sequence because it is the Heinz number of the partition [2,3]; (ii) 10 (= 2*5) is not in the sequence because it is the Heinz number of the partition [1,3]. - Emeric Deutsch, Oct 02 2015

Except for the term 1, each term can uniquely represented as A002110(k)/A002110(m) for k > m >= 0; 1 = A002110(k)/A002110(k) for all k. - Michel Marcus and Jianing Song, Jun 19 2019

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

FORMULA

a(n) ~ n log n. - Charles R Greathouse IV, Oct 24 2012

EXAMPLE

105 is a term, as 105 = 3*5*7 with consecutive prime factors.

MAPLE

isA073485 := proc(n)

    local plist, p, i ;

    plist := sort(convert(numtheory[factorset](n), list)) ;

    for i from 1 to nops(plist) do

        p := op(i, plist) ;

        if modp(n, p^2) = 0 then

            return false;

        end if;

        if i > 1 then

            if nextprime(op(i-1, plist)) <> p then

                return false;

            end if;

        end if;

    end do:

    true;

end proc:

for n from 1 to 1000 do

    if isA073485(n) then

        printf("%d, ", n);

    end if;

end do: # R. J. Mathar, Jan 12 2016

MATHEMATICA

f[n_] := FoldList[ Times, 1, Prime[ Range[n, n + 3]]]; lst = {}; k = 1; While[k < 55, AppendTo[lst, f@k]; k++ ]; Take[ Union@ Flatten@ lst, 65] (* Robert G. Wilson v, Jun 11 2010 *)

PROG

(Haskell)

a073485 n = a073485_list !! (n-1)

a073485_list = filter ((== 1) . a192280) [1..]

-- Reinhard Zumkeller, May 28 2012, Aug 26 2011

(PARI) list(lim)=my(v=List(primes(primepi(lim))), p, t); for(e=2, log(lim+.5)\log(2), p=1; t=prod(i=1, e-1, prime(i)); forprime(q=prime(e), lim, t*=q/p; if(t>lim, next(2)); listput(v, t); p=nextprime(p+1))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Oct 24 2012

CROSSREFS

Complement: A193166.

Intersection of A005117 and A073491.

Subsequence of A277417.

Cf. A053590, A073483, A073484, A073486, A192280.

Cf. A000040, A006094, A002110, A097889, A169829 (subsequences).

Sequence in context: A308420 A260442 A098962 * A062101 A330597 A283599

Adjacent sequences:  A073482 A073483 A073484 * A073486 A073487 A073488

KEYWORD

nonn,nice,changed

AUTHOR

Reinhard Zumkeller, Aug 03 2002

EXTENSIONS

Alternative description added to the name by Antti Karttunen, Oct 29 2016

STATUS

approved

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Last modified February 24 09:21 EST 2020. Contains 332209 sequences. (Running on oeis4.)