A036328 Composite numbers n such that juxtaposition of prime factors of n has length 4.

16, 24, 36, 40, 44, 52, 54, 56, 60, 66, 68, 76, 78, 81, 84, 90, 92, 99, 100, 102, 110, 114, 116, 117, 121, 124, 126, 130, 135, 138, 140, 143, 148, 150, 153, 154, 164, 165, 169, 170, 171, 172, 174, 182, 186, 187, 188, 189, 190, 195, 196, 202, 206, 207, 209, 210

Offset: 1

Author

Patrick De Geest, Dec 15 1998

Keywords

• nonn
• base
• fini
• full
• easy

Comments

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

Prime factors are taken with multiplicity. - Harvey P. Dale, Dec 05 2015

Links

• Nathaniel Johnston, Table of n, a(n) for n = 1..1048 (full sequence)

Crossrefs

Cf. A036326-A036334.

Programs

Maple

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

Mathematica

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