A190381 Numbers with prime factorization pqrstuv^2.

1021020, 1141140, 1381380, 1492260, 1531530, 1711710, 1741740, 1763580, 1806420, 1861860, 2018940, 2072070, 2134860, 2222220, 2238390, 2277660, 2386020, 2434740, 2462460, 2545620, 2552550, 2582580, 2612610, 2645370, 2691780, 2709630

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, May 09 2011

Keywords

• nonn

Links

• T. D. Noe, Table of n, a(n) for n = 1..1000
• Will Nicholes, Prime Signatures
• Index to sequences related to prime signature

Crossrefs

Cf. A190378, A190380.

Programs

Mathematica

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

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