

A204518


Numbers such that floor(a(n)^2 / 6) is a square.


19



0, 1, 2, 3, 5, 10, 27, 49, 98, 267, 485, 970, 2643, 4801, 9602, 26163, 47525, 95050, 258987, 470449, 940898, 2563707, 4656965, 9313930, 25378083, 46099201, 92198402, 251217123, 456335045, 912670090, 2486793147, 4517251249, 9034502498, 24616714347
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,3


COMMENTS

Or: Numbers such that their square, with its last base6 digit dropped, is again a square. (For the three initial terms whose square has only one digit in base 6, this is then meant to yield zero.)


LINKS

Table of n, a(n) for n=1..34.
Index entries for linear recurrences with constant coefficients, signature (0,0,10,0,0,1).


FORMULA

a(n) = sqrt(A055851(n)).
a(n) = 10*a(n3)a(n6) for n>7; G.f.: x^2*(x+1)*(3*x^4+7*x^32*x^2x1) / (x^610*x^3+1).  Colin Barker, Sep 18 2014


PROG

(PARI) b=6; for(n=0, 2e9, issquare(n^2\b) & print1(n", "))
(PARI) concat(0, Vec(x^2*(x+1)*(3*x^4+7*x^32*x^2x1)/(x^610*x^3+1) + O(x^100))) \\ Colin Barker, Sep 18 2014


CROSSREFS

Cf. A023110 (base 10), A204502 (base 9), A204514 (base 8), A204516 (base 7), A204520 (base 5), A004275 (base 4), A055793 (base 3), A055792 (base 2).
Sequence in context: A011833 A007695 A133662 * A223545 A088938 A000617
Adjacent sequences: A204515 A204516 A204517 * A204519 A204520 A204521


KEYWORD

nonn,easy


AUTHOR

M. F. Hasler, Jan 15 2012


EXTENSIONS

More terms from Colin Barker, Sep 18 2014


STATUS

approved



