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A099475 Number of divisors d of n such that d+2 is also a divisor of n. 5
0, 0, 1, 1, 0, 1, 0, 1, 1, 0, 0, 3, 0, 0, 2, 1, 0, 1, 0, 1, 1, 0, 0, 4, 0, 0, 1, 1, 0, 2, 0, 1, 1, 0, 1, 3, 0, 0, 1, 2, 0, 1, 0, 1, 2, 0, 0, 4, 0, 0, 1, 1, 0, 1, 0, 1, 1, 0, 0, 5, 0, 0, 2, 1, 0, 1, 0, 1, 1, 1, 0, 4, 0, 0, 2, 1, 0, 1, 0, 2, 1, 0, 0, 4, 0, 0, 1, 1, 0, 2, 0, 1, 1, 0, 0, 4, 0, 0, 2, 1, 0, 1, 0, 1, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,12

COMMENTS

0 <= a(n) <= a(m*n) for all m>0;

a(A099477(n)) = 0; a(A059267(n)) > 0;

a(A099476(n)) = n and a(m) <> n for m < A099476(n).

For n>0: a(A008585(n))>0, a(A008586(n))>0 and a(A008588(n))>0.

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

MAPLE

A099475:= proc(n)

local d;

  d:= numtheory:-divisors(n);

nops(d intersect map(`+`, d, 2))

end proc:

map(A099475, [$1..1000]); # Robert Israel, Jun 19 2015

MATHEMATICA

a[n_] := DivisorSum[n, Boole[Divisible[n, #+2]]&]; Array[a, 105] (* Jean-Fran├žois Alcover, Dec 07 2015 *)

PROG

(PARI) A099475(n) = { sumdiv(n, d, ! (n % (d+2))) } \\ Michel Marcus, Jun 18 2015

CROSSREFS

Cf. A007862 (similar but with d+1 instead).

Sequence in context: A096936 A115979 A067168 * A120569 A128113 A108930

Adjacent sequences:  A099472 A099473 A099474 * A099476 A099477 A099478

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Oct 18 2004

STATUS

approved

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Last modified October 20 12:47 EDT 2019. Contains 328257 sequences. (Running on oeis4.)