login
This site is supported by donations to The OEIS Foundation.

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A204516 Numbers such that floor(a(n)^2 / 7) is a square. 19
0, 1, 2, 3, 8, 16, 45, 127, 254, 717, 2024, 4048, 11427, 32257, 64514, 182115, 514088, 1028176, 2902413, 8193151, 16386302, 46256493, 130576328, 261152656, 737201475, 2081028097, 4162056194, 11748967107, 33165873224, 66331746448 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Or: Numbers whose square, with its last base-7 digit dropped, is again a square (where for the first 3 terms, dropping the digit is meant to yield zero).

LINKS

Table of n, a(n) for n=1..30.

M. F. Hasler, Truncated squares, OEIS wiki, Jan 16 2012

Index to sequences related to truncating digits of squares.

FORMULA

G.f. = (x + 2*x^2 + 3*x^3 - 8*x^4 - 16*x^5 - 3*x^6 )/(1 - 16*x^3 + x^6).

floor(a(n)^2 / 7) = A204517(n)^2.

PROG

(PARI) b=7; for(n=0, 2e9, issquare(n^2\b) & print1(n", "))

CROSSREFS

Cf. A031149 (base 10), A204502 (base 9), A204514 (base 8), A204518 (base 6), A004275=sqrt(A055808) (base 4), A001075=sqrt(A055793) (base 3), A001541=sqrt(A055792) (base 2).

Sequence in context: A032104 A051573 A292853 * A277346 A005648 A113947

Adjacent sequences:  A204513 A204514 A204515 * A204517 A204518 A204519

KEYWORD

nonn,changed

AUTHOR

M. F. Hasler, Jan 15 2012

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 January 18 04:47 EST 2019. Contains 319269 sequences. (Running on oeis4.)