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a(n) = smallest k such that for each r, 2 <= r <= n, there exists a distinct s, n < s <= k, with the same prime signature as r.
(history; published version)
#5 by N. J. A. Sloane at Thu Dec 05 19:56:31 EST 2013
AUTHOR

_Amarnath Murthy (amarnath_murthy(AT)yahoo.com), _, Sep 13 2003

Discussion
Thu Dec 05
19:56
OEIS Server: https://oeis.org/edit/global/2075
#4 by Russ Cox at Sat Mar 31 13:20:50 EDT 2012
FORMULA

For sufficiently large n, a(n) = 7^floor(log(n)/log(3)) because log(prime(2m))/log(prime(m)) is largest for m = 2. - _David Wasserman (wasserma(AT)spawar.navy.mil), _, Jun 03 2005

EXTENSIONS

More terms from _David Wasserman (wasserma(AT)spawar.navy.mil), _, Jun 03 2005

Discussion
Sat Mar 31
13:20
OEIS Server: https://oeis.org/edit/global/880
#3 by N. J. A. Sloane at Fri May 19 03:00:00 EDT 2006
FORMULA

For sufficiently large n, a(n) = 7^floor(log(n)/log(3)), because log(prime(2m))/log(prime(m)) is largest for m = 2. - David Wasserman (wasserma(AT)spawar.navy.mil), Jun 03 2005

KEYWORD

nonn,new

nonn

#2 by N. J. A. Sloane at Tue Jul 19 03:00:00 EDT 2005
NAME

a(n) = smallest k such that for every each r, 2= <= r= <= n , there exists an a distinct s, n < s <= k , with the same prime signature of as r.

DATA

3, 5, 7, 9, 11, 13, 13, 19, 27, 49, 49, 49, 49, 49, 49, 49, 81, 81, 81, 81, 81, 81, 81, 81, 81, 169, 169, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 361, 361, 361, 361, 361, 361, 361, 361, 361, 361, 361

COMMENTS

Question: Find an ( the best possible) estimate of a(n) in terms of n. Conjecture: a(prime(r)^k) = prime(2r)^k.

FORMULA

For sufficiently large n, a(n) = 7^floor(log(n)/log(3)), because log(prime(2m))/log(prime(m)) is largest for m = 2. - David Wasserman (wasserma(AT)spawar.navy.mil), Jun 03 2005

EXAMPLE

a(7) = 19 and For numbers ( 2,3,4,5,6,7) we have the set of numbers ( 11,13,9,17,10,19) with matching prime signatures.

( 11,13,9,17,10,19) with matching prime signatures.

KEYWORD

more,nonn,new

nonn

EXTENSIONS

More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Jun 03 2005

#1 by N. J. A. Sloane at Thu Feb 19 03:00:00 EST 2004
NAME

a(n) = smallest k such that for every r, 2=<r=<n there exists an s, n<s<=k with the prime signature of r.

DATA

3, 5, 9, 11, 13, 19, 27, 49, 49, 49, 49, 49, 49, 49, 81, 81, 81, 81, 81, 81, 81, 81

OFFSET

2,1

COMMENTS

Question: Find an ( the best possible) estimate of a(n) in terms of n. Conjecture: a(prime(r)^k) = prime(2r)^k.

EXAMPLE

a(7) = 19 and For numbers ( 2,3,4,5,6,7) we have the set of numbers

( 11,13,9,17,10,19) with matching prime signatures.

KEYWORD

more,nonn

AUTHOR

Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Sep 13 2003

STATUS

approved