|
%I #16 Jun 09 2023 08:15:19
%S 0,1,2,2,3,3,3,6,6,3,5,5,3,9,12,4,5,5,5,15,9,3,7,14,6,9,15,5,7,7,5,15,
%T 9,9,24,8,3,9,21,7,7,7,5,25,15,3,9,18,10,15,15,5,7,21,21,21,9,3,11,11,
%U 3,15,30,18,21,7,5,15,21,7,11,11,3,15,25,15,21,7,9,36,12,3,11,33,9,9,21,7
%N a(n) = number of divisors of n(n+1) that divide neither n nor n+1.
%H Antti Karttunen, <a href="/A175454/b175454.txt">Table of n, a(n) for n = 1..16385</a>
%F a(n) = (d(n)-1)*(d(n+1)-1), where d(n) = A000005(n).
%o (PARI) A175454(n)={ local(a=0) ; fordiv(n*(n+1),d, if(n %d <>0 && (n+1)%d<> 0, a++ ) ; ) ; return(a) ; }
%o { for(n=1,120, print1(A175454(n)",") ; ) ; } \\ _R. J. Mathar_, May 28 2010
%o (PARI) A175454(n) = ((numdiv(n)-1)*(numdiv(n+1)-1)); \\ _Antti Karttunen_, Oct 07 2017, after the given formula.
%Y Cf. A000005.
%K nonn
%O 1,3
%A _Leroy Quet_, May 16 2010
%E More terms from _Jon E. Schoenfield_ and _R. J. Mathar_, May 28 2010
|
