A083532 First difference sequence of A007369. Differences between impossible values for sum of divisors of n.

3, 4, 1, 1, 5, 1, 2, 2, 1, 1, 2, 1, 1, 2, 4, 1, 1, 2, 4, 2, 2, 1, 1, 2, 1, 1, 1, 1, 2, 3, 1, 2, 3, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 3, 2, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 2, 2, 1, 1, 1, 1, 3, 1, 2, 4, 1, 1, 3, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 1, 2, 2, 2, 2, 2, 1, 1, 2, 1, 2, 1

Offset

1,1

Links

Table of n, a(n) for n=1..105.

Formula

a(n) = A007369(n+1) - A007369(n).

Example

29 and 33 are the 15th and 16th nonsense values for sigma(x), since there exist no numbers n of which they are sums of divisors, while {30,31,32} equal sigma(x); e.g., for x = 29, 16, 31, respectively, thus 33 - 29 = 4 = a(15) = A007369(16) - A007369(15).

Mathematica

t0[x_] := Table[j, {j, 1, x}]; t=Table[DivisorSigma[1, w], {w, 1, 25000}]; u=Union[%]; c=Complement[t0[25000], u]; Delete[c-RotateRight[c], 1]

Crossrefs

Cf. A002191, A007369, A083531, A083533, A083534, A083535, A083536.

Sequence in context: A238550 A275886 A158572 * A073366 A001086 A105283

Adjacent sequences: A083529 A083530 A083531 * A083533 A083534 A083535

Keyword

nonn

Author

Labos Elemer, May 20 2003

Status

approved