1,3

Antti Karttunen, Table of n, a(n) for n = 1..16385

a(n) = (d(n)-1)*(d(n+1)-1), where d(n) = A000005(n).

(PARI) A175454(n)={ local(a=0) ; fordiv(n*(n+1), d, if(n %d <>0 && (n+1)%d<> 0, a++ ) ; ) ; return(a) ; }

{ for(n=1, 120, print1(A175454(n)", ") ; ) ; } \\ R. J. Mathar, May 28 2010

(PARI) A175454(n) = ((numdiv(n)-1)*(numdiv(n+1)-1)); \\ Antti Karttunen, Oct 07 2017, after the given formula.

Sequence in context: A293924 A307730 A169618 * A157501 A080968 A115733

Adjacent sequences: A175451 A175452 A175453 * A175455 A175456 A175457

nonn

Leroy Quet, May 16 2010

More terms from Jon E. Schoenfield and R. J. Mathar, May 28 2010

approved