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

 

Logo

Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A260908 Numerator of 1/det(M) where M is the n X n matrix with M[i,j] = 1/gcd(i,j). 1
1, -2, 3, -12, 15, 45, -105, 420, -1890, -4725, 10395, 31185, -135135, -315315, -4729725, 4729725, -80405325, -723647925, 1527701175, 7638505875, 53469541125, 117632990475, -245959889175, -737879667525, 18446991688125, 79936963981875, -2158298027510625 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Negative terms for n: 2, 4, 7, 9, 10, 13, 14, 15, 17, 18, 23, 24, 27, 28, 30, ..., .

LINKS

Table of n, a(n) for n=1..27.

MATHEMATICA

f[n_] := 1/Det[ Table[ 1/GCD[i, j], {i, n}, {j, n}]]; Numerator@ Array[f, 27]

PROG

(PARI) vector(40, n, numerator(1/matdet(matrix(n, n, i, j, 1/gcd(i, j))))) \\ Michel Marcus, Aug 06 2015

CROSSREFS

Cf. A060841, A260909.

Sequence in context: A067780 A290168 A124486 * A123761 A181121 A333319

Adjacent sequences:  A260905 A260906 A260907 * A260909 A260910 A260911

KEYWORD

sign

AUTHOR

Robert G. Wilson v, Aug 04 2015

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 December 1 05:52 EST 2020. Contains 338833 sequences. (Running on oeis4.)