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!)
A328045 a(n) = smallest m for which there is a sequence n = b_1 < b_2 < ... < b_t = m such that b_1^c_1*b_2^c_2*...*b_t^c_t is a fourth power, with all c_i < 4. 3

%I

%S 0,1,4,6,4,10,9,14,15,9,18,22,20,26,21,24,16,34,27,38,25,28,33,46,30,

%T 25,39,35,36,58,40,62,42,44,51,45,36,74,57,52,49,82,50,86,55,54,69,94,

%U 54,49,63,68,65,106,70,66,64,76,87,118,75,122,93,77,64,78

%N a(n) = smallest m for which there is a sequence n = b_1 < b_2 < ... < b_t = m such that b_1^c_1*b_2^c_2*...*b_t^c_t is a fourth power, with all c_i < 4.

%C a(n) = n if and only if n is a perfect square.

%C a(n) >= n + A300518(n) if n is not a perfect square.

%C a(n) <= A006255(n), and a(n) = A006255(n) except for when n is in A328218, a subsequence of A269045.

%H Peter Kagey, <a href="/A328045/b328045.txt">Table of n, a(n) for n = 0..500</a>

%e For n = 1, a(1) = 1 with sequence 1 = 1^4.

%e For n = 2, a(2) = 4 with sequence 2^2 * 4 = 2^4.

%e For n = 3, a(3) = 6 with sequence 3^2 * 4 * 6^2 = 6^4.

%e For n = 4, a(4) = 4 with sequence 4^2 = 2^4.

%e For n = 5, a(5) = 10 with sequence 5 * 8^3 * 10^3 = 40^4.

%e For n = 6, a(6) = 9 with sequence 6^2 * 8^2 * 9 = 12^4.

%e For n = 7, a(7) = 14 with sequence 7^2 * 8^2 * 14^2 = 28^4.

%Y Cf. A006255 (square), A277494 (cube).

%Y Cf. A269045, A300518, A328218.

%K nonn,more

%O 0,3

%A _Peter Kagey_, Oct 02 2019

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 July 14 19:48 EDT 2020. Contains 335729 sequences. (Running on oeis4.)