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

1,1

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)

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 *)

Prog

(PARI) lista(nn) = {forstep(n=2, nn, 2, if (numdiv(n) < numdiv(n+1), print1(n, ", ")); ); } \\ Michel Marcus, Apr 10 2015
(GAP) Filtered([2, 4..1300], n->Tau(n)<Tau(n+1)); # Muniru A Asiru, Apr 05 2018

Crossrefs

Cf. A000005, A138046, A138171.

Sequence in context: A047823 A294738 A044997 * A074772 A074771 A342258

Adjacent sequences: A138169 A138170 A138171 * A138173 A138174 A138175

Keyword

nonn

Author

Leroy Quet, Mar 03 2008

Status

approved