A036328 - OEIS

%I #12 Feb 21 2019 23:16:50

%S 16,24,36,40,44,52,54,56,60,66,68,76,78,81,84,90,92,99,100,102,110,

%T 114,116,117,121,124,126,130,135,138,140,143,148,150,153,154,164,165,

%U 169,170,171,172,174,182,186,187,188,189,190,195,196,202,206,207,209,210

%N Composite numbers n such that juxtaposition of prime factors of n has length 4.

%C The last term of this sequence is a(1048)=9409.

%C Prime factors are taken with multiplicity. - _Harvey P. Dale_, Dec 05 2015

%H Nathaniel Johnston, <a href="/A036328/b036328.txt">Table of n, a(n) for n = 1..1048</a> (full sequence)

%p isA036328 := proc(n) local d: d:=ifactors(n)[2]: return `if`(not isprime(n) and add(length(d[j][1])*d[j][2], j=1..nops(d))=4, n, NULL): end: l:=[seq(isA036328(n),n=2..9999)]; # _Nathaniel Johnston_, Jun 22 2011

%t jpf4Q[n_]:=Length[Flatten[IntegerDigits/@Table[#[[1]],{#[[2]]}]&/@FactorInteger[n]]]==4; Select[Range[300],jpf4Q] (* _Harvey P. Dale_, Dec 05 2015 *)

%Y Cf. A036326-A036334.

%K nonn,base,fini,full,easy

%O 1,1

%A _Patrick De Geest_, Dec 15 1998