A080650 Numbers n such that phi(n) and sigma(n) have the same number of divisors.

1, 4, 7, 18, 19, 21, 39, 41, 45, 72, 77, 99, 103, 124, 133, 137, 143, 147, 153, 171, 172, 194, 199, 215, 231, 242, 247, 261, 268, 275, 287, 288, 307, 309, 320, 327, 335, 336, 349, 350, 363, 364, 366, 372, 399, 434, 436, 477, 490, 491, 551, 575, 597, 605, 639

Offset

1,2

Links

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

Mathematica

Select[Range[10^3], DivisorSigma[0, DivisorSigma[1, # ]] == DivisorSigma[0, EulerPhi[ # ]] &]

Crossrefs

Cf. A000005, A000010, A000203.

Sequence in context: A057450 A077274 A292850 * A276187 A357041 A318025

Adjacent sequences: A080647 A080648 A080649 * A080651 A080652 A080653

Keyword

nonn

Author

Joseph L. Pe, Feb 28 2003

Status

approved