login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A173706 Triangle read by rows, of p*(q-1) for primes p, q with p>q. 2
3, 5, 10, 7, 14, 28, 11, 22, 44, 66, 13, 26, 52, 78, 130, 17, 34, 68, 102, 170, 204, 19, 38, 76, 114, 190, 228, 304, 23, 46, 92, 138, 230, 276, 368, 414, 29, 58, 116, 174, 290, 348, 464, 522, 638, 31, 62, 124, 186, 310, 372, 496, 558, 682, 868 (list; table; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
The crossing number of a (p,q) torus knot with p > q => 2 is p*(q-1) [Proposition 10.5.3 in Cromwell]
REFERENCES
Peter R. Cromwell, Knots and Links, Cambridge University Press, November 15, 2004, p. 255.
LINKS
FORMULA
T(i,j) = prime(i) * (prime(j)-1) = A000040(i) * (A000040(j)-1) = A000040(i) * A006093(j).
EXAMPLE
3;
5, 10;
7, 14, 28;
11, 22, 44, 66;
13, 26, 52, 78, 130;
17, 34, 68, 102, 170, 204;
MAPLE
T:= (i, j)-> ithprime(i) *(ithprime(j)-1): seq (seq (T(n, k), k=1..n-1), n=2..11);
MATHEMATICA
Table[Prime[i]*(Prime[j] - 1), {n, 2, 10}, {k, 1, n - 1}] // Flatten (* G. C. Greubel, Nov 23 2016 *)
CROSSREFS
Sequence in context: A083519 A302088 A211414 * A365440 A332359 A328070
KEYWORD
nonn,easy,tabl
AUTHOR
Jonathan Vos Post, Nov 25 2010
EXTENSIONS
Edited by Alois P. Heinz, Nov 25 2010
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)