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A258929 a(n) is the unique even-valued 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 (list; graph; refs; listen; history; text; internal format)
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 values--one even, the other odd. This sequence gives the even residue. (The odd residues are in A259266.)

LINKS

Table of n, a(n) for n=1..24.

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

Cf. A048898, A048899, A257366, A259266.

Sequence in context: A232155 A112365 A242200 * A034959 A316902 A316904

Adjacent sequences:  A258926 A258927 A258928 * A258930 A258931 A258932

KEYWORD

nonn

AUTHOR

Jon E. Schoenfield, Jun 15 2015

EXTENSIONS

More terms and additional comments from Jon E. Schoenfield, Jun 23 2015

STATUS

approved

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Last modified August 7 19:57 EDT 2020. Contains 336279 sequences. (Running on oeis4.)