login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A264887 Numbers in A007504 such that omega(a(n)) = Omega(a(n)) = 4. 2

%I

%S 5830,6870,13490,16401,58406,60146,61910,65534,75130,136114,148827,

%T 153178,213538,257358,269074,273054,327198,354102,377310,382038,

%U 403611,443685,475323,488774,496905,665130,684510,691026,799846,817563

%N Numbers in A007504 such that omega(a(n)) = Omega(a(n)) = 4.

%C Omega and omega are given in A001221 and A001222, respectively.

%C The corresponding numbers of prime summands, k(n), are 53, 57, 77, 84, 149, 151, 153, 157, 167, 219, 228, 231, 269, 293, 299, 301, 327, 339, 349, 351, 360, 376, 388, 393, 396, 453, 459, 461, 493, 498, ...

%C Intersection of A007504 and A046386 (products of four distinct primes). - _Michel Marcus_, Dec 15 2015

%H John Cerkan, <a href="/A264887/b264887.txt">Table of n, a(n) for n = 1..10000</a>

%e For n = 1, k(n) = 53 and a(n) = A007504(53) = 5830 = 2*5*11*53.

%e For n = 2, k(n) = 57 and a(n) = A007504(57) = 6870 = 2*3*5*229.

%e For n = 3, k(n) = 77 and a(n) = A007504(77) = 13490 = 2*5*19*71.

%e For n = 4, k(n) = 84 and a(n) = A007504(84) = 16401 = 3*7*11*71.

%e For n = 5, k(n) = 149 and a(n) = A007504(149) = 58406 = 2*19*29*53.

%e For n = 6, k(n) = 151 and a(n) = A007504(151) = 60146 = 2*17*29*61.

%e Note that for each of the elements of the sequence, omega(a(n)) = Omega(a(n)) = 4, i.e., the number of prime factors of a(n) = the number of distinct prime factors of a(n) = 4.

%t t = Accumulate@ Prime@ Range@ 600; Select[t, PrimeNu@ # == PrimeOmega@ # == 4 &] (* _Michael De Vlieger_, Nov 27 2015, after _Zak Seidov_ at A007504 *)

%o (PARI) lista(nn) = {my(s = 0); for (n=1, nn, s += prime(n); if ((omega(s) == 4) && (bigomega(s)==4), print1(s, ", ")););} \\ _Michel Marcus_, Nov 28 2015

%Y Cf. A001221, A001222, A007504, A013918, A046386, A189072, A264885.

%K nonn

%O 1,1

%A _Debapriyay Mukhopadhyay_, Nov 27 2015

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 May 24 10:48 EDT 2019. Contains 323529 sequences. (Running on oeis4.)