

A258929


a(n) is the unique evenvalued residue modulo 5^n of a number m such that m^2+1 is divisible by 5^n.


1



2, 18, 68, 182, 1068, 1068, 32318, 280182, 280182, 3626068, 23157318, 120813568, 1097376068, 1097376068, 11109655182, 49925501068, 355101282318, 355101282318, 15613890344818, 15613890344818, 365855836217682, 2273204469030182, 2273204469030182, 49956920289342682
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OFFSET

1,1


COMMENTS

For any positive integer n, if a number of the form m^2+1 is divisible by 5^n, then m mod 5^n must take one of two valuesone even, the other odd. This sequence gives the even residue. (The odd residues are in A259266.)


LINKS



EXAMPLE

If m^2+1 is divisible by 5, then m mod 5 is either 2 or 3; the even value is 2, so a(1)=2.
If m^2+1 is divisible by 5^2, then m mod 5^2 is either 7 or 18; the even value is 18, so a(2)=18.
If m^2+1 is divisible by 5^3, then m mod 5^3 is either 57 or 68; the even value is 68, so a(3)=68.


CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS



STATUS

approved



