A073033 A 4-cycle of the k => sigma(k)-k process, where sigma(k) is the sum of divisors of k (A000203).

18656380, 20522060, 28630036, 24289964, 18656380, 20522060, 28630036, 24289964, 18656380, 20522060, 28630036, 24289964, 18656380, 20522060, 28630036, 24289964, 18656380, 20522060, 28630036, 24289964, 18656380, 20522060, 28630036, 24289964

Offset: 1

Author

Miklos Kristof, Aug 22 2002

Keywords

• nonn
• easy

Comments

18656380 = 2^2*5*932819, 20522060 = 2^2*5*13*17*4643, 28630036 = 2^2*19*449*839, 24289964 = 2^2*97*62603.

The cycle was discovered by Cohen (1970). - Amiram Eldar, Aug 18 2024

Links

• Henri Cohen, On amicable and sociable numbers, Math. Comp., Vol. 24, No. 110 (1970), pp. 423-429.
• Index entries for linear recurrences with constant coefficients, signature (0,0,0,1).

Crossrefs

Cf. A000203, A073032, A090615.

Programs

PARI

a(n)=[24289964, 18656380, 20522060, 28630036][n%4+1] \\ Charles R Greathouse IV, Feb 19 2013