A073032 A 4-cycle of the k => sigma(k)-k process, where sigma(k) is the sum of divisors of k (A000203).

18048976, 20100368, 18914992, 19252208, 18048976, 20100368, 18914992, 19252208, 18048976, 20100368, 18914992, 19252208, 18048976, 20100368, 18914992, 19252208, 18048976, 20100368, 18914992, 19252208, 18048976, 20100368, 18914992, 19252208, 18048976

Offset: 1

Author

Miklos Kristof, Aug 22 2002

Keywords

• nonn
• easy

Comments

18048976 = 2^4*11*102551, 20100368 = 2^4*919*1367, 18914992 = 2^4*37*89*359, 19252208 = 2^4*1203263.

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, A045477, A073033, A090615.

Programs

PARI

a(n)=[19252208, 18048976, 20100368, 18914992][n%4+1] \\ Charles R Greathouse IV, Feb 19 2013

Extensions

Terms corrected by Charles R Greathouse IV, Feb 19 2013