login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A245036 a(n) = 4*prime(n)^3 - 27*prime(n)^2 = (prime(n)^2)*[4*prime(n) - 27], n >= 4. 2
49, 2057, 4225, 11849, 17689, 34385, 74849, 93217, 165649, 230297, 268105, 355649, 519665, 727529, 807457, 1081849, 1295537, 1412185, 1803649, 2101145, 2606009, 3396649, 3845777, 4084465, 4591049, 4859329, 5426825, 7758049, 8529017, 9778649, 10220809, 12632369, 13156177, 14814049 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,1

COMMENTS

The discriminant D of the solution of the Cardano-Tartaglia equation x^3 + p*x + q = 0 is written D = -27*q^2 - 4*p^3. Let q = p = -prime(n) then D = -27*prime(n)^2 - 4*[-prime(n)]^3 = 4*[prime(n)]^3 - 27*prime(n)^2 = (prime(n)^2)*[4*prime(n) - 27], D > 0, n >= 4. a(n) = -D, offset 4,1. Remark: a(1) = -76, a(2) = -135, a(3) = -175.

Because in the preceding comment q can also be taken as +prime(n) this shows that the equation x^3 - prime(n)*x - prime(n) = 0 as well as x^3 - prime(n)*x + prime(p) = 0 has for each n >= 4 three distinct real solutions. - Wolfdieter Lang, Jul 29 2014

LINKS

Freimut Marschner, Table of n, a(n) for n = 4..6320

FORMULA

a(n) = 4*[prime(n)]^3 - 27*prime(n)^2 = (prime(n)^2)*[4*prime(n) - 27], n >= 4.

EXAMPLE

n = 6, prime(6) = 13, 13^2*(4*13 - 27) = 4225.

MATHEMATICA

4#^3-27#^2&/@Prime[Range[4, 40]] (* Harvey P. Dale, Feb 08 2021 *)

CROSSREFS

Cf. A000040 (prime(n)), A001248 (prime(n)^2), A030078 (prime(n)^3).

Sequence in context: A260856 A065785 A163927 * A061615 A049682 A162914

Adjacent sequences:  A245033 A245034 A245035 * A245037 A245038 A245039

KEYWORD

nonn

AUTHOR

Freimut Marschner, Jul 10 2014

EXTENSIONS

Name and Data have been changed to be in accordance to the Cardano-Tartaglia discriminant.

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 22 14:25 EDT 2021. Contains 347607 sequences. (Running on oeis4.)