

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 base7 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


AUTHOR

M. F. Hasler, Jan 15 2012


STATUS

approved



