This site is supported by donations to The OEIS Foundation.



(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A240986 Determinants of n X n matrices of sets of distinct primes selected by increasing prime gaps (see comments). 1
3, 6, -36, -216, 1296, -5184, -145152, -3856896, -170325504, -6133211136, 1094593056768, 26742290558976, -497681937801216, -14357497419546624, 657148066947072000, 12008320398059765760, 1322255096225695531008, 70546799432003423698944, -6537119853797882157072384, -27940593871362459110473728 (list; graph; refs; listen; history; text; internal format)



Let P = {3,5,7,11,...} be the sequence of odd primes and let P(k) = {prime in P: (prime+2k) is in P} (although set builder notation is used for P(k) we will still assume that P(k) is a sequence). Let M(n) be the n X n matrix where row 1 is the first n elements from P(1), row 2 is the first n elements from P(2), and in general row j is the first n elements from P(j). This sequence is the sequence of determinants for M(1), M(2), M(3), M(4), ..., M(9).


Table of n, a(n) for n=1..20.

Samuel J. Erickson, Python Code

Sachin Joglekar, Determinant of matrix of any order (Python)


For the first element of the sequence we find the determinant of the matrix [[3,5],[3,7]], where [3,5] is row 1 and [3,7] is row 2. These numbers are there because in row 1 we are looking at the primes where we can add 2 to get another prime; 3+2 is prime and so is 5+2, so they go in row 1. Similarly, for the second row we get [3,7] because these are the first primes such that when 4 is added we get a prime: 3+4 and 7+4 are both prime, so they go in row 2. For the second entry in the sequence we take the determinant of [[3,5,11],[3,7,13],[5,7,11]]; the reason we get [5,7,11] in the third row is because 5 is the first prime where 5+6 is prime, 7 is second prime where 7+6 is prime, and 11 is the third prime where 11+6 is prime.


(Python) See link for code.

(PARI) a(n) = {my(m=matrix(n, n), j); for (i=1, n, j = 1; forprime(p=2, , if (isprime(p+2*i), m[i, j] = p; j++); if (j > n, break); ); ); matdet(m); } \\ Michel Marcus, May 04 2019


Cf. A001359, A023200, A023201, A023202, A023203.

Sequence in context: A068084 A003674 A211895 * A120595 A048642 A264702

Adjacent sequences:  A240983 A240984 A240985 * A240987 A240988 A240989




Samuel J. Erickson, Aug 06 2014


Offset 1 and more terms from Michel Marcus, May 04 2019



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 October 15 01:40 EDT 2019. Contains 328025 sequences. (Running on oeis4.)