A035479 (-1)sigma sequence: a(n) = (-1)sigma(a(n-1)), where if (-1)sigma(k) = A049060(k) and a(1) = 624.

624, 696, 728, 936, 1716, 1200, 1682, 869, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480

Offset: 1

Author

Yasutoshi Kohmoto

Keywords

• nonn

Comments

This sequence becomes a cycle of period 3: 780, 480, 488. It is called a (-1)sigma sociable group of order 3.

Examples

			Factorizations: 2^4*3*13, 2^3*3*29, 2^3*7*13, 2^3*3^2*13, 2^2*3*11*13,  2^4*3*5^2, 2*29^2, 11*79, 2^2*3*5*13, 2^5*3*5, 2^3*61.
		

Crossrefs

Cf. A049060.

Programs

Mathematica

f[p_, e_] := (p^(e + 1) - 1)/(p - 1) - 2; s[n_] := Times @@ f @@@ FactorInteger[n]; s[1] = 1; NestList[s, 624, 50] (* Amiram Eldar, Aug 26 2022 *)

Extensions

Offset corrected by Amiram Eldar, Aug 26 2022