A014390 - OEIS

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A014390

Final 2 digits of 7^n.

1, 7, 49, 43, 1, 7, 49, 43, 1, 7, 49, 43, 1, 7, 49, 43, 1, 7, 49, 43, 1, 7, 49, 43, 1, 7, 49, 43, 1, 7, 49, 43, 1, 7, 49, 43, 1, 7, 49, 43, 1, 7, 49, 43, 1, 7, 49, 43, 1, 7, 49, 43, 1, 7, 49, 43, 1, 7, 49, 43, 1, 7, 49, 43, 1, 7

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for sequences related to final digits of numbers

Index entries for linear recurrences with constant coefficients, signature (1,-1,1).

FORMULA

a(n) = 7^n mod 50. [Zerinvary Lajos, Nov 27 2009]

MATHEMATICA

PowerMod[7, Range[0, 70], 100] (* Harvey P. Dale, Jan 23 2012 *)

LinearRecurrence[{1, -1, 1}, {1, 7, 49}, 70] (* Harvey P. Dale, May 09 2018 *)

PROG

(Sage) [power_mod(7, n, 50)for n in range(0, 80)] # Zerinvary Lajos, Nov 27 2009

(PARI) a(n)=lift(Mod(7, 100)^n) \\ Charles R Greathouse IV, Jan 02 2013

(Magma) [Modexp(7, n, 100): n in [0..110]]; // Vincenzo Librandi, Aug 16 2016

CROSSREFS

Sequence in context: A317014 A330329 A115589 * A043070 A083930 A178367

Adjacent sequences: A014387 A014388 A014389 * A014391 A014392 A014393

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved