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!)
A230389 Least k such that n! + k^2 + k is a perfect square. 1
0, 0, 1, 5, 3, 119, 719, 260, 180, 495, 3628799, 39916799, 6561647, 9899, 722799, 15308432, 735092, 779904000, 1193692724, 77841862127, 1947879910469375, 7981643124, 231453720692, 37427202522827, 1793894810624, 251579908188224, 286527829489835787, 33866880878997899 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

a(n) <= n!-1, because with k=n!-1 we have n!+k^2+k = n! + (n!)^2 - 2*n! + 1 + n! - 1 = (n!)^2, a perfect square.

LINKS

Jon E. Schoenfield, Table of n, a(n) for n = 0..42

EXAMPLE

4! + 3^2+3 = 24+12 = 36, a perfect square, so a(4)=3.

CROSSREFS

Cf. A000290, A000142, A002378.

Sequence in context: A145985 A180403 A267512 * A048885 A264738 A002208

Adjacent sequences:  A230386 A230387 A230388 * A230390 A230391 A230392

KEYWORD

nonn

AUTHOR

Alex Ratushnyak, Oct 18 2013

EXTENSIONS

a(18)-a(21) from Jon E. Schoenfield, Oct 24 2013

a(22) from Jon E. Schoenfield, Oct 26 2013

a(23) from Jon E. Schoenfield, Oct 29 2013

More terms from Jon E. Schoenfield, Nov 26 2013

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 00:42 EDT 2020. Contains 337276 sequences. (Running on oeis4.)