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Integer part of the square root of sigma(n).
2

%I #9 Nov 18 2017 09:07:08

%S 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,

%T 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,

%U 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

%N Integer part of the square root of sigma(n).

%H Antti Karttunen, <a href="/A078705/b078705.txt">Table of n, a(n) for n = 1..16384</a>

%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>

%F a(n) = A000196(A000203(n)). - _Antti Karttunen_, Nov 18 2017

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

%o (Scheme) (define (A078705 n) (A000196 (A000203 n))) ;; [For the implementations of A000196 and A000203, see under the respective entries]. - _Antti Karttunen_, Nov 18 2017

%o (PARI) a(n) = sqrtint(sigma(n)); \\ _Michel Marcus_, Nov 18 2017

%Y Cf. A000196, A000203.

%K easy,nonn,look

%O 1,3

%A _Joseph L. Pe_, Dec 18 2002