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A240171 Numbers n such that n has more divisors than n-1. 1
2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 24, 26, 28, 30, 32, 36, 38, 40, 42, 44, 48, 50, 52, 54, 56, 60, 62, 63, 64, 66, 68, 70, 72, 74, 75, 78, 80, 84, 88, 90, 92, 96, 98, 100, 102, 104, 108, 110, 112, 114, 116, 120, 122, 124, 126, 128, 130, 132, 135, 138, 140 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n such that A051950(n) > 0. - Robert Israel, Aug 03 2014

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

22 has the same number of divisors as 21 (both have 4 divisors,) so 22 does not qualify for this sequence. 63 has 6 divisors, and 62 has only 4, so 63 qualifies.

MAPLE

N:= 1000: # to get all entries <= N

L:= map(numtheory:-tau, [$1..N]):

A:= select(t -> L[t] > L[t-1], [$2..N]); # Robert Israel, Aug 03 2014

MATHEMATICA

Flatten[Position[Partition[DivisorSigma[0, Range[200]], 2, 1], _?(#[[1]]< #[[2]]&), {1}, Heads->False]]+1 (* Harvey P. Dale, Feb 08 2015 *)

PROG

(PARI)

for(n=1, 10^3, if(numdiv(n)>numdiv(n-1), print1(n, ", "))) \\ Derek Orr, Aug 02 2014

CROSSREFS

Cf. A000005, A051950.

Sequence in context: A059548 A064720 A029741 * A221284 A272670 A234521

Adjacent sequences:  A240168 A240169 A240170 * A240172 A240173 A240174

KEYWORD

nonn,easy

AUTHOR

J. Lowell, Aug 02 2014

STATUS

approved

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Last modified June 21 09:08 EDT 2021. Contains 345358 sequences. (Running on oeis4.)