A030984 2-automorphic numbers: final digits of 2*n^2 agree with n.

8, 88, 688, 4688, 54688, 554688, 3554688, 93554688, 893554688, 893554688, 40893554688, 40893554688, 40893554688, 70040893554688, 870040893554688, 1870040893554688, 71870040893554688, 871870040893554688

Offset

1,1

Comments

a(n) is the unique positive integer less than 10^n such that a(n) is divisible by 2^n and 2*a(n) - 1 is divisible by 5^n. - Eric M. Schmidt, Aug 18 2012

Links

Eric M. Schmidt, Table of n, a(n) for n = 1..1000

Eric Weisstein's World of Mathematics, Automorphic Number

Index entries for sequences related to automorphic numbers

Index entries for sequences related to final digits of numbers

Prog

(Sage) [crt(0, (5^n + 1)/2, 2^n, 5^n) for n in range(1, 1001)] # Eric M. Schmidt, Aug 18 2012

Crossrefs

Sequence in context: A299749 A300263 A367278 * A109021 A271939 A043043

Adjacent sequences: A030981 A030982 A030983 * A030985 A030986 A030987

Keyword

nonn,base

Author

Eric W. Weisstein

Status

approved