|
|
A230766
|
|
Numbers with more than one prime factor and, in the ordered factorization, the exponent never decreases when read from left to right.
|
|
2
|
|
|
6, 10, 14, 15, 18, 21, 22, 26, 30, 33, 34, 35, 36, 38, 39, 42, 46, 50, 51, 54, 55, 57, 58, 62, 65, 66, 69, 70, 74, 75, 77, 78, 82, 85, 86, 87, 91, 93, 94, 95, 98, 100, 102, 105, 106, 108, 110, 111, 114, 115, 118, 119, 122, 123, 129, 130, 133, 134, 138, 141
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
LINKS
|
|
|
FORMULA
|
If n = prod_{k=1..m} p(k)^e(k), then m > 1 and e(1) <= e(2) <= ... <= e(m).
|
|
MATHEMATICA
|
fQ[n_] := Module[{f = Transpose[FactorInteger[n]][[2]]}, Length[f] > 1 && Min[Differences[f]] >= 0]; Select[Range[2, 200], fQ] (* T. D. Noe, Nov 04 2013 *)
Select[Range[150], PrimeNu[#]>1&&Min[Differences[FactorInteger[#][[All, 2]]]]>=0&] (* Harvey P. Dale, May 22 2020 *)
|
|
PROG
|
(PARI) isok(n) = {my(f = factor(n), nbf = #f~); if (nbf < 2, return (0)); lastexp = 0; for (i=1, nbf, if ((newexp = f[i, 2]) < lastexp, return (0)); lastexp = newexp; ); return (1); } \\ Michel Marcus, Oct 30 2013
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|