A082772 Integers n such that there exists at least one divisor d of n, 1 < d < n, such that d divides n and d+1 divides n+1.

8, 14, 15, 20, 24, 26, 27, 32, 35, 38, 39, 44, 48, 50, 51, 56, 62, 63, 64, 65, 68, 74, 75, 80, 84, 86, 87, 90, 92, 95, 98, 99, 104, 110, 111, 116, 119, 120, 122, 123, 124, 125, 128, 132, 134, 135, 140, 143, 144, 146, 147, 152, 155, 158, 159, 164, 168, 170, 171, 174

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

24 is a term since 4 divides 24 and 5 divides 25.

Mathematica

aQ[n_] := AnyTrue[Most @ Rest @ Divisors[n], Divisible[n+1, #+1] &]; Select[ Range[2, 200], aQ ] (* Amiram Eldar, Sep 18 2019 *)

Prog

(C++) for (int a = 1; a < 200; a++) for (int b = 2; b < a; b++) if ((a%b==0)&&((a+1)%(b+1)==0)) cout << a << ", "; // outputs a
(PARI) isok(n) = {fordiv(n, d, if ((d>1) && (d<n) && ! ((n+1) % (d+1)), return (1)); ); } \\ Michel Marcus, Sep 18 2019

Crossrefs

Sequence in context: A236295 A178838 A219303 * A103338 A250004 A114456

Adjacent sequences: A082769 A082770 A082771 * A082773 A082774 A082775

Keyword

easy,nonn

Author

Anne M. Donovan (anned3005(AT)aol.com), May 21 2003

Status

approved