A160811 Numbers not dividing 24.

5, 7, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77

Offset

1,1

Comments

These terms m > 5 can be called "triphile" or "3-phile" numbers, because there are 3 positive integers b_1 < b_2 < b_3 such that b_1 divides b_2, b_2 divides b_3 and m = b_1 + b_2 + b_3. A number that is not "triphile" is called "triphobe" or "3-phobe" (A019532). The smallest triphile number is 7 = 1 + 2 + 4 and the largest triphobe is 24. See A348517 for more explanations and link. - Bernard Schott, Oct 21 2021

Links

Table of n, a(n) for n=1..69.

Omar E. Pol, Determinacion geometrica de los numeros primos y perfectos

Omar E. Pol, Divisors and pi(x)

Index entries for linear recurrences with constant coefficients, signature (2,-1).

Formula

a(n) = n + 8 for n > 16. [Charles R Greathouse IV, Oct 26 2011]

Mathematica

Complement[Range[100], Divisors[24]] (* Harvey P. Dale, May 13 2019 *)

Prog

(PARI) is(n)=!!n%24 \\ Charles R Greathouse IV, Oct 26 2011

Crossrefs

Complement of A018253.

Cf. A000005, A000720, A161205.

Cf. A019532, A348517.

Sequence in context: A143730 A354454 A194394 * A116451 A126949 A079696

Adjacent sequences: A160808 A160809 A160810 * A160812 A160813 A160814

Keyword

easy,nonn

Author

Omar E. Pol, Jun 19 2009, Jun 28 2009

Extensions

Definition corrected by Omar E. Pol, Nov 17 2009

Status

approved