login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A330681 a(n) = A283980(A025487(n)). 3
1, 6, 36, 30, 216, 180, 1296, 1080, 210, 7776, 900, 6480, 1260, 46656, 5400, 38880, 7560, 279936, 32400, 6300, 233280, 2310, 27000, 45360, 1679616, 194400, 37800, 1399680, 13860, 162000, 272160, 10077696, 1166400, 226800, 8398080, 83160, 972000, 44100, 1632960, 60466176, 189000, 6998400, 69300, 810000, 1360800 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

After 1, contains only the least representatives of such prime signatures where the maximal exponent occurs more than once. However, here the terms are not in ascending order.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..15703

FORMULA

a(n) = A283980(A025487(n)).

A046523(a(n)) = a(n).

A085089(a(n)) = A101296(a(n)) = A330683(n).

EXAMPLE

For example, 180 = 2^2 * 3^2 * 5^1 is present, because the maximal exponent in its prime factorization is 2, which occurs as an exponent of both 2 and 3, and because 180 is the minimal representative of the prime signature (2,2,1), as A046523(180) = 180.

PROG

(PARI)

A283980(n) = {my(f=factor(n)); prod(i=1, #f~, my(p=f[i, 1], e=f[i, 2]); if(p==2, 6, nextprime(p+1))^e)}; \\ From A283980

A025487list(e) = { my(lista = List([1, 2]), i=2, u = 2^e, t); while(lista[i] != u, if(2*lista[i] <= u, listput(lista, 2*lista[i]); t = A283980(lista[i]); if(t <= u, listput(lista, t))); i++); vecsort(Vec(lista)); }; \\ Returns a list of terms up to the term 2^e.

v025487 = A025487list(64);

A025487(n) = v025487[n];

A330681(n) = A283980(A025487(n));

CROSSREFS

Cf. A025487, A046523, A283980, A329899, A330683.

Sequence in context: A001311 A137868 A070401 * A070400 A222929 A222784

Adjacent sequences:  A330678 A330679 A330680 * A330682 A330683 A330684

KEYWORD

nonn

AUTHOR

Antti Karttunen, Dec 26 2019

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 11 23:38 EDT 2021. Contains 342895 sequences. (Running on oeis4.)