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!)
A280935 Numbers k such that k = rad(k) * sopfr(k), where rad(k) is the squarefree kernel of k and sopfr(k) the integer log of k. 1

%I

%S 16,27,72,540,2106,2625,3264,5445,5824,5880,10647,13475,15210,15500,

%T 18048,22800,28611,37752,38528,39445,42237,47334,61568,64141,68952,

%U 69575,70308,71136,71478,72912,74115,75392,79000,80937,83712,89775,100156,100359,113680,114660

%N Numbers k such that k = rad(k) * sopfr(k), where rad(k) is the squarefree kernel of k and sopfr(k) the integer log of k.

%H Paolo P. Lava, <a href="/A280935/b280935.txt">Table of n, a(n) for n = 1..500</a>

%e Prime factors of 2106 are 2, 3, 3, 3, 3, 13. Then rad(2106) = 2 * 3 * 13 = 78, sopfr(2106) = 2 + 3 + 3 + 3 + 3 + 13 = 27 and 78 * 27 = 2106.

%p with(numtheory): P:=proc(q) local a,k,n; for n from 1 to q do a:=ifactors(n)[2];

%p if n=mul(a[k][1],k=1..nops(a))*add(a[k][1]*a[k][2],k=1..nops(a)) then print(n);

%p fi; od; end: P(10^9);

%Y Cf. A001414, A007947, A068999.

%K nonn,easy

%O 1,1

%A _Paolo P. Lava_, Jan 11 2017

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 September 19 10:53 EDT 2021. Contains 347556 sequences. (Running on oeis4.)