A098220 a(n) = floor(sigma(sigma(p))/p) = floor(sigma(p+1)/p) = floor(A008333(n)/p), where p is the n-th prime number.

2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 1, 2, 1, 2, 2, 2, 1, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1, 1, 1, 2, 2, 3, 1, 2, 1, 2, 2, 1, 2, 2, 1, 2, 3, 1, 2, 2, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 1, 2, 2, 2, 3, 2, 1, 2, 2, 2, 1, 2, 1, 3, 1, 2, 1, 2, 2, 2, 1, 2, 2, 2, 3, 1, 2, 2, 3, 2, 2, 1, 1, 1, 2, 2, 2, 2

Offset: 1

Author

Labos Elemer, Oct 25 2004

Keywords

• nonn

Comments

Values of these quotients are expectedly lower than ratios of A051027(n)/n.

Examples

			For n = 7, the seventh prime is 17, so a(7) = floor(sigma(sigma(17))/17) = floor(sigma(18)/17) = floor(39/17) = 2.
		

Crossrefs

Cf. A000203, A051027, A008333, A098219, A098221, A098222.

Programs

PARI

a(n) = my(p=prime(n)); sigma(p+1)\p; \\ Michel Marcus, Dec 23 2018