A064992 - OEIS

A064992

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

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..1000

FORMULA

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

PROG

(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

CROSSREFS

Cf. A034448.

Sequence in context: A069777 A225816 A227655 * A187783 A089759 A325970

Adjacent sequences: A064989 A064990 A064991 * A064993 A064994 A064995

KEYWORD

sign

AUTHOR

N. J. A. Sloane, Oct 31 2001

STATUS

approved