A188631 Numbers k such that d(k-1) < d(k) < d(k+1) where d(k) is the number of divisors of k.

62, 63, 74, 164, 188, 194, 195, 207, 255, 275, 278, 279, 284, 314, 356, 362, 363, 398, 399, 404, 422, 423, 428, 455, 458, 459, 483, 494, 524, 539, 584, 614, 615, 662, 674, 692, 734, 747, 758, 759, 764, 824, 854, 867, 890, 927, 935, 944, 956, 998, 999

Offset: 1

Author

Juri-Stepan Gerasimov, Apr 05 2011

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000005, A188540, A075028.

Programs

Magma

d:=func; [ n: n in [2..1000] | d(n-1) lt d(n) and d(n) lt d(n+1)]; // Bruno Berselli, Apr 05 2011

Mathematica

Select[Range[2,1000], DivisorSigma[0, # - 1] < DivisorSigma[0, #] < DivisorSigma[0, # + 1] &] (* T. D. Noe, Apr 05 2011 *)

Formula

A000005(a(n)-1) < A000005(a(n)) < A000005(a(n)+1).

Extensions

Corrected and extended by T. D. Noe, Apr 05 2011