A138172 Even n where d(n) < d(n+1), where d(n) = number of positive divisors of n.

62, 74, 134, 146, 164, 188, 194, 206, 254, 274, 278, 284, 314, 356, 362, 386, 398, 404, 422, 428, 454, 458, 482, 494, 524, 538, 554, 566, 584, 614, 626, 662, 674, 692, 734, 746, 758, 764, 794, 818, 824, 854, 866, 890, 914, 926, 934, 944, 956, 974, 998, 1004, 1028

Offset: 1

Author

Leroy Quet, Mar 03 2008

Keywords

• nonn

Comments

Terms calculated by M. F. Hasler.

First term == 0 (mod 6) is a(133) = 2274. - Jianing Song, Apr 03 2018

Links

• Jianing Song and Muniru A Asiru, Table of n, a(n) for n = 1..10000(Terms 1 through 1019 from Jianing Song)

Crossrefs

Cf. A000005, A138046, A138171.

Programs

GAP

Filtered([2,4..1300],n->Tau(n)Muniru A Asiru, Apr 05 2018

Maple

with(numtheory): A138172:=n->`if`(n mod 2 = 0 and tau(n) < tau(n+1), n, NULL): seq(A138172(n), n=1..1000); # Wesley Ivan Hurt, Apr 10 2015

Mathematica

2 Position[Partition[Array[DivisorSigma[0, #] &, 10^3, 2], 2, 2], ?(#1 < #2 & @@ # &)][[All, 1]] (* _Michael De Vlieger, Apr 07 2018 *)

PARI

lista(nn) = {forstep(n=2, nn, 2, if (numdiv(n) < numdiv(n+1), print1(n, ", ")););} \\ Michel Marcus, Apr 10 2015