

A327302


One of the two successive approximations up to 5^n for the 5adic integer sqrt(9). This is the 1 (mod 5) case (except for n = 0).


3



0, 1, 21, 46, 546, 3046, 12421, 59296, 59296, 840546, 8653046, 28184296, 125840546, 369981171, 2811387421, 2811387421, 2811387421, 460575059296, 2749393418671, 10378787949921, 48525760606171, 143893192246796, 2051241825059296, 6819613407090546, 30661471317246796
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OFFSET

0,3


COMMENTS

a(n) is the unique number k in [1, 5^n] and congruent to 1 mod 5 such that k^2 + 9 is divisible by 5^n.


LINKS



FORMULA

a(1) = 1; for n >= 2, a(n) is the unique number k in {a(n1) + m*5^(n1) : m = 0, 1, 2, 3, 4} such that k^2 + 9 is divisible by 5^n.
For n > 0, a(n) = 5^n  A327303(n).


EXAMPLE

The unique number k in {1, 6, 11, 16, 21} such that k^2 + 9 is divisible by 25 is k = 21, so a(2) = 21.
The unique number k in {21, 46, 71, 96, 121} such that k^2 + 9 is divisible by 125 is k = 46, so a(3) = 46.
The unique number k in {46, 171, 296, 421, 546} such that k^2 + 9 is divisible by 625 is k = 546, so a(4) = 546.


PROG

(PARI) a(n) = truncate(sqrt(9+O(5^n)))


CROSSREFS

Approximations of 5adic square roots:


KEYWORD

nonn


AUTHOR



STATUS

approved



