A069062 Numbers k such that k^2-1 and k^2+1 have the same number of positive divisors.

2, 3, 12, 30, 42, 60, 68, 102, 108, 112, 123, 128, 162, 168, 198, 200, 212, 213, 252, 294, 302, 312, 318, 333, 336, 338, 372, 387, 447, 448, 450, 462, 498, 502, 522, 542, 578, 592, 598, 600, 606, 612, 648, 672, 678, 708, 717, 752, 762, 795, 808, 810, 812

Offset

1,1

Links

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

Mathematica

Select[Range[1000], DivisorSigma[0, #^2 - 1] == DivisorSigma[0, #^2 + 1] &] (* Amiram Eldar, Jun 04 2022 *)

Prog

(PARI) isok(n) = numdiv(n^2-1) == numdiv(n^2+1); \\ Michel Marcus, Nov 24 2013

Crossrefs

Cf. A000005, A002522, A005563, A193432, A347191.

Sequence in context: A260631 A195913 A048085 * A356017 A025560 A073618

Adjacent sequences: A069059 A069060 A069061 * A069063 A069064 A069065

Keyword

easy,nonn

Author

Benoit Cloitre, Apr 04 2002

Status

approved