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A069062
Numbers k such that k^2-1 and k^2+1 have the same number of positive divisors.
6
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
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
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 04 2002
STATUS
approved