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A179644 Product of the 4th power of a prime and 2 different distinct primes (p^4*q*r). 14


%S 240,336,528,560,624,810,816,880,912,1040,1104,1134,1232,1360,1392,

%T 1456,1488,1520,1776,1782,1840,1904,1968,2064,2106,2128,2256,2288,

%U 2320,2480,2544,2576,2754,2832,2835,2928,2960,2992,3078,3216,3248,3280,3344,3408

%N Product of the 4th power of a prime and 2 different distinct primes (p^4*q*r).

%H T. D. Noe, <a href="/A179644/b179644.txt">Table of n, a(n) for n = 1..1000</a>

%H <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>

%e 240=2^4*3*5,336=2^4*3*7,..810=2^3^4*5,..

%p op(select(n->nops(factorset(n))=3 and sort([seq(op(2, a), a=ifactors(n)[2])])=[1,1,4], [$1..3408])); # _Paolo P. Lava_, Jul 18 2019

%t f[n_]:=Sort[Last/@FactorInteger[n]]=={1,1,4}; Select[Range[4000], f]

%t Take[Union[#[[1]]^4 #[[2]]#[[3]]&/@(Flatten[Permutations/@ Subsets[ Prime[ Range[ 20]],{3}],1])],50] (* _Harvey P. Dale_, Feb 07 2013 *)

%o (PARI) list(lim)=my(v=List(),t);forprime(p=2,(lim\6)^(1/4),forprime(q=2,sqrt(lim\p^4),if(p==q,next);t=p^4*q;forprime(r=q+1,lim\t,if(p==r,next);listput(v,t*r))));vecsort(Vec(v)) \\ _Charles R Greathouse IV_, Jul 19 2011

%Y Cf. A006881, A007304, A065036, A085986, A085987, A178739, A179642, A179643.

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Jul 21 2010

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Last modified August 11 23:45 EDT 2020. Contains 336434 sequences. (Running on oeis4.)