A064992 - OEIS

%I #11 Jun 19 2018 05:17:58

%S 2,1,1,1,6,-4,1,1,8,-6,8,-6,10,0,-7,1,12,-10,10,2,4,-12,12,-10,16,-14,

%T 12,-10,42,-40,1,15,6,-6,2,-12,22,-4,-2,-12,54,-52,16,0,12,-24,20,-18,

%U 28,-6,-2,-16,30,-12,0,8,10,-30,60,-58,34,-16,-15,19,60,-76,22,6,48,-72,18,-16,40

%N a(n) = usigma(n+1) - usigma(n), where usigma(n) is the sum of unitary divisors of n (A034448).

%H Harry J. Smith, <a href="/A064992/b064992.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = A034448(n+1) - A034448(n).

%o (PARI) usigma(n)= { local(f,s=1); f=factor(n); for(i=1, matsize(f)[1], s*=1 + f[i, 1]^f[i, 2]); return(s) } { u=1; for (n=1, 1000, u1=usigma(n + 1); a=u1 - u; u=u1; write("b064992.txt", n, " ", a) ) } \\ _Harry J. Smith_, Oct 02 2009

%Y Cf. A034448.

%K sign

%O 1,1

%A _N. J. A. Sloane_, Oct 31 2001