A030990 7-automorphic numbers ending in 3: final digits of 7n^2 agree with n.

3, 43, 143, 7143, 57143, 857143, 2857143, 42857143, 142857143, 7142857143, 57142857143, 857142857143, 2857142857143, 42857142857143, 142857142857143, 7142857142857143, 57142857142857143

Offset

1,1

Comments

a(n) is the unique positive integer less than 10^n such that 7a(n) - 1 is divisible by 10^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

Index entries for linear recurrences with constant coefficients, signature (11,-10,-1000,11000,-10000).

Mathematica

LinearRecurrence[{11, -10, -1000, 11000, -10000}, {3, 43, 143, 7143, 57143}, 20] (* Harvey P. Dale, Apr 02 2018 *)

Prog

(Sage) [inverse_mod(7, 10^n) for n in range(1, 1001)] # Eric M. Schmidt, Aug 18 2012

Crossrefs

Sequence in context: A003525 A042661 A281503 * A306970 A376737 A054698

Adjacent sequences: A030987 A030988 A030989 * A030991 A030992 A030993

Keyword

nonn,base

Author

Eric W. Weisstein

Status

approved