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A188629
Numbers k such that k^2 has one more divisor than k^2 - 1.
2
2, 4, 8, 14, 16, 22, 38, 58, 135, 158, 178, 256, 297, 382, 502, 542, 568, 676, 718, 878, 1202, 1215, 1312, 1318, 1382, 1438, 1593, 1622, 1822, 2018, 2144, 2336, 2558, 2578, 2744, 2858, 2902, 3062, 3118, 3296, 3375, 3778, 3993, 4023, 4064, 4192, 4282
OFFSET
1,1
LINKS
MAPLE
isA188629 := proc(n) if numtheory[tau](n^2) = numtheory[tau](n^2-1)+1 then true; else false; end if; end proc:
for n from 1 do if isA188629(n) then print(n) ; end if; end do: # R. J. Mathar, Apr 14 2011
MATHEMATICA
Select[Range[10000], DivisorSigma[0, #^2 - 1] + 1 == DivisorSigma[0, #^2] &]
PROG
(PARI) is(k) = k > 1 && numdiv(k^2-1) + 1 == numdiv(k^2); \\ Amiram Eldar, Apr 17 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved