A078705 Integer part of the square root of sigma(n).

1, 1, 2, 2, 2, 3, 2, 3, 3, 4, 3, 5, 3, 4, 4, 5, 4, 6, 4, 6, 5, 6, 4, 7, 5, 6, 6, 7, 5, 8, 5, 7, 6, 7, 6, 9, 6, 7, 7, 9, 6, 9, 6, 9, 8, 8, 6, 11, 7, 9, 8, 9, 7, 10, 8, 10, 8, 9, 7, 12, 7, 9, 10, 11, 9, 12, 8, 11, 9, 12, 8, 13, 8, 10, 11, 11, 9, 12, 8, 13, 11, 11, 9, 14, 10, 11, 10, 13, 9, 15, 10, 12, 11

Offset: 1

Author

Joseph L. Pe, Dec 18 2002

Keywords

• easy
• nonn
• look

Links

• Antti Karttunen, Table of n, a(n) for n = 1..16384
• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000196, A000203.

Programs

Mathematica

Table[Floor[Sqrt[DivisorSigma[1, i]]], {i, 1, 100}]

PARI

a(n) = sqrtint(sigma(n)); \\ Michel Marcus, Nov 18 2017

Scheme

(define (A078705 n) (A000196 (A000203 n))) ;; [For the implementations of A000196 and A000203, see under the respective entries]. - Antti Karttunen, Nov 18 2017

Formula

a(n) = A000196(A000203(n)). - Antti Karttunen, Nov 18 2017