A053858 Squarefree even composite numbers with an odd number of prime factors.

30, 42, 66, 70, 78, 102, 110, 114, 130, 138, 154, 170, 174, 182, 186, 190, 222, 230, 238, 246, 258, 266, 282, 286, 290, 310, 318, 322, 354, 366, 370, 374, 402, 406, 410, 418, 426, 430, 434, 438, 442, 470, 474, 494, 498, 506, 518, 530, 534, 574, 582, 590

Offset

1,1

Comments

Prime factors counted with multiplicity. - Harvey P. Dale, May 21 2024

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

a(3)=66 because 66 is even and its prime divisors are 2, 3 and 11, an odd number.

Maple

ts_m2_sod := proc(n); if (numtheory[mobius](n)=-1 and isprime(n)='false' and type(n, even)='true') then RETURN(n); fi end: am2sod := [seq(ts_m2_sod(i), i=1..2500)]: am2sod;

Mathematica

Select[Range[2, 602, 2], CompositeQ[#]&&SquareFreeQ[#]&&OddQ[PrimeOmega[#]]&] (* Harvey P. Dale, May 21 2024 *)

Prog

(PARI) is(n, f=factor(n))=n%2==0 && #f[, 2]>2 && vecmax(f[, 2])==1 && (#f[, 2])%2 \\ Charles R Greathouse IV, Aug 29 2017

Crossrefs

A075819 is a subsequence. Intersection of A026424, A039956, and A002808.

Sequence in context: A093599 A007304 A160350 * A075819 A306217 A034683

Adjacent sequences: A053855 A053856 A053857 * A053859 A053860 A053861

Keyword

easy,nonn

Author

Enoch Haga, Mar 28 2000

Extensions

Name corrected by Charles R Greathouse IV, Aug 29 2017

Status

approved