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A216093 a(n) = 10^n - (5^(2^n) mod 10^n). 7
5, 75, 375, 9375, 9375, 109375, 7109375, 87109375, 787109375, 1787109375, 81787109375, 81787109375, 81787109375, 40081787109375, 740081787109375, 3740081787109375, 43740081787109375, 743740081787109375 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
a(n)^3 mod 10^n = a(n).
a(n) is the unique positive integer less than 10^n such that a(n) is divisible by 5^n and a(n) + 1 is divisible by 2^n. - Eric M. Schmidt, Sep 01 2012
a(n+1) + a(n)^2 == 0 (mod 10^(n+1)). - Robert Israel, Apr 24 2017
LINKS
FORMULA
2^(4*5^(n-1)) mod 10^n - 1.
MAPLE
f:= n -> (-5 &^(2^n) mod 10^n):
map(f, [$1..30]); # Robert Israel, Apr 24 2017
PROG
(Sage) def A216093(n) : return crt(-1, 0, 2^n, 5^n) # Eric M. Schmidt, Sep 01 2012
CROSSREFS
Sequence in context: A285452 A048350 A030991 * A151752 A127212 A091903
KEYWORD
nonn
AUTHOR
V. Raman, Sep 01 2012
STATUS
approved

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Last modified February 25 11:10 EST 2024. Contains 370324 sequences. (Running on oeis4.)