login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A190381 Numbers with prime factorization pqrstuv^2. 1

%I #11 May 20 2017 11:45:17

%S 1021020,1141140,1381380,1492260,1531530,1711710,1741740,1763580,

%T 1806420,1861860,2018940,2072070,2134860,2222220,2238390,2277660,

%U 2386020,2434740,2462460,2545620,2552550,2582580,2612610,2645370,2691780,2709630

%N Numbers with prime factorization pqrstuv^2.

%H T. D. Noe, <a href="/A190381/b190381.txt">Table of n, a(n) for n = 1..1000</a>

%H Will Nicholes, <a href="http://willnicholes.com/math/primesiglist.htm">Prime Signatures</a>

%H <a href="/index/Pri#prime_signature">Index to sequences related to prime signature</a>

%t f[n_]:=Sort[Last/@FactorInteger[n]]=={1,1,1,1,1,1,2};Select[Range[3000000],f]

%o (PARI) list(lim)=my(v=List(),t1,t2,t3,t4,t5,t6); forprime(p1=2,sqrtint(lim\30030), t1=p1^2; forprime(p2=2,lim\(2310*t1), if(p2==p1, next); t2=p2*t1; forprime(p3=2,lim\(210*t2), if(p3==p1 || p3==p2, next); t3=p3*t2; forprime(p4=2,lim\(30*t3), if(p4==p1 || p4==p2 || p4==p3, next); t4=p4*t3; forprime(p5=2,lim\(6*t4), if(p5==p1 || p5==p2 || p5==p3 || p5==p4, next); t5=p5*t4; forprime(p6=2,lim\(2*t5), if(p6==p1 || p6==p2 || p6==p3 || p6==p4 || p6==p5, next); t6=p6*t5; forprime(p7=2,lim\t6, if(p7==p1 || p7==p2 || p7==p3 || p7==p4 || p7==p5 || p7==p6, next); listput(v, t6*p7)))))))); Set(v) \\ _Charles R Greathouse IV_, Aug 25 2016

%Y Cf. A190378, A190380.

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, May 09 2011

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 16 18:24 EDT 2024. Contains 375977 sequences. (Running on oeis4.)