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A059992 Numbers with an increasing number of nonprime divisors. 3
1, 4, 8, 12, 24, 36, 48, 60, 72, 120, 180, 240, 360, 720, 840, 1080, 1260, 1440, 1680, 2160, 2520, 4320, 5040, 7560, 10080, 15120, 20160, 25200, 27720, 30240, 45360, 50400, 55440, 75600, 83160, 110880, 151200, 166320, 221760, 277200, 332640 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Positions of records in A033273.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..571 (terms 1..146 from Ray Chandler)

EXAMPLE

a(4)=12 because twelve has 4 nonprime divisors {1, 4, 6 and 12} whereas a(3)=8 has only 3; and twelve is the first number greater than eight which exhibits this property.

MATHEMATICA

l = 0; Do[ c = Count[PrimeQ[ Divisors[n] ], False]; If[c > l, l = c; Print[n] ], {n, 1, 10^6} ]

PROG

(PARI) lista(nn) = {my(m=0, nb); for (n=1, nn, nb = sumdiv(n, d, !isprime(d)); if (nb > m, m = nb; print1(n, ", ")); ); } \\ Michel Marcus, Jul 16 2019

CROSSREFS

Cf. A055079, A002182, A033273, A180040.

Sequence in context: A272708 A157416 A278602 * A050570 A233341 A102110

Adjacent sequences:  A059989 A059990 A059991 * A059993 A059994 A059995

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Mar 08 2001

EXTENSIONS

Alternate description and b-file from Ray Chandler, Aug 07 2010

STATUS

approved

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Last modified October 23 14:54 EDT 2019. Contains 328345 sequences. (Running on oeis4.)