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A138171
Odd n where d(n) > d(n+1), where d(n) = number of positive divisors of n.
4
45, 81, 105, 117, 165, 225, 261, 273, 297, 315, 325, 333, 345, 357, 385, 405, 435, 441, 465, 477, 495, 513, 525, 555, 561, 567, 585, 595, 621, 625, 627, 651, 675, 693, 705, 715, 765, 777, 795, 801, 825, 837, 855, 861, 885, 891, 897, 915, 925, 945, 957, 975
OFFSET
1,1
COMMENTS
Terms calculated by M. F. Hasler.
First term == 5 (mod 6) is a(385) = 6125. - Jianing Song, Apr 03 2018
LINKS
MAPLE
with(numtheory): a:=proc(n) if tau(2*n)<tau(2*n-1) then 2*n-1 else end if end proc: seq(a(n), n=1..500); # Emeric Deutsch, Mar 12 2008
with(numtheory): a:=proc (n) if `mod`(n, 2)=1 and tau(n+1) < tau(n) then n else end if end proc: seq(a(n), n=1..1000); # Emeric Deutsch, Mar 31 2008
MATHEMATICA
Select[Range[1, 1001, 2], DivisorSigma[0, #]>DivisorSigma[0, #+1]&] (* Harvey P. Dale, Jul 08 2017 *)
PROG
(PARI) isok(n) = (n%2) && (numdiv(n) > numdiv(n+1)); \\ Michel Marcus, Apr 04 2018
(PARI) lista(nn) = forstep(n=1, nn, 2, if(numdiv(n) > numdiv(n+1), print1(n, ", "))); \\ Altug Alkan, Apr 04 2018
(GAP) Filtered([1, 3..1301], n->Tau(n)>Tau(n+1)); # Muniru A Asiru, Apr 05 2018
CROSSREFS
Sequence in context: A364718 A102578 A026060 * A305154 A280407 A063343
KEYWORD
nonn
AUTHOR
Leroy Quet, Mar 03 2008
STATUS
approved