The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
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!)
A110278 Values of n such that the perfect deficiency (A109883) of n and n+1 are both squares. 1
1, 4, 5, 16, 37, 256, 65536, 80656, 3459600, 166926400 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Conjecture: sequence is infinite.
No more terms below 10^9. - Amiram Eldar, Dec 27 2018
LINKS
EXAMPLE
A109883(37)=36 & A109883(38)=16, both of which are squares, so 37 is a term.
MATHEMATICA
subtract = If[ #1 < #2, Throw[ #1], #1 - #2]&; f[n_] := Catch @ Fold[subtract, n, Divisors @ n]; a = False; Do[b = IntegerQ[ Sqrt[ f[ n]]]; If[{a, b} == {True, True}, Print[n - 1]]; a = b, {n, 10^7}] (* Robert G. Wilson v, Jul 21 2005 *)
PROG
(PARI) a109883(n) = {my(r = n); fordiv(n, d, if (r < d, return (r)); r -= d; ); 0; }
isok(n) = issquare(a109883(n)) && issquare(a109883(n+1)); \\ Michel Marcus, Dec 28 2018
CROSSREFS
Cf. A110277.
Sequence in context: A352156 A284869 A057729 * A013628 A127007 A007837
KEYWORD
more,nonn
AUTHOR
Jason Earls, Jul 18 2005
EXTENSIONS
a(10) from Amiram Eldar, Dec 27 2018
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 May 27 13:56 EDT 2024. Contains 372861 sequences. (Running on oeis4.)