1,1

d is a unitary divisor of n if gcd(d,n/d)=1; usigma(n) is their sum (A034448).

The prime factors of a unitary perfect number (A002827) are the Higgs primes (A057447). - Paul Muljadi (paulmuljadi(AT)yahoo.com), Oct 10 2005

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

R. K. Guy, Unsolved Problems in Number Theory, Sect. B3.

D. S. Mitrinovic et al., Handbook of Number Theory, Kluwer, Section III.45.1.

M. V. Subbarao, T. J. Cook, R. S. Newberry and J. M. Weber, On unitary perfect numbers, Delta, 3 (No. 1, 1972), 22-26.

C. R. Wall, The fifth unitary perfect number, Canad. Math. Bull., 18 (1975), 115-122.

C. R. Wall, On the largest odd component of a unitary perfect number, Fib. Quart., 25 (1987), 312-316.

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

G. Villemin's Almanac of Numbers, Nombres Unitairement Parfaits

Wikipedia, Unitary perfect number

Unitary divisors of 60 are 1,4,3,5,12,20,15,60, with sum 120 = 2*60.

146361946186458562560000 = 2^18 * 3 * 5^4 * 7 * 11 * 13 * 19 * 37 * 79 * 109 * 157 * 313

Cf. A034460, A034448.

Cf. A002827, A057447.

Adjacent sequences: A002824 A002825 A002826 this_sequence A002828 A002829 A002830

Sequence in context: A074452 A007358 A007357 this_sequence A137498 A036283 A126576

nonn,nice,hard

N. J. A. Sloane (njas(AT)research.att.com).