A224473 - OEIS

A224473

(2*5^(2^n) - 1) mod 10^n: a sequence of trimorphic numbers ending in 9.

9, 49, 249, 1249, 81249, 781249, 5781249, 25781249, 425781249, 6425781249, 36425781249, 836425781249, 9836425781249, 19836425781249, 519836425781249, 2519836425781249, 12519836425781249, 512519836425781249, 4512519836425781249, 84512519836425781249

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OFFSET

1,1

COMMENTS

a(n) is the unique positive integer less than 10^n such that a(n) - 1 is divisible by 2^n and a(n) + 1 is divisible by 5^n.

LINKS

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

Eric Weisstein's World of Mathematics, Trimorphic Number

Index entries for sequences related to automorphic numbers

FORMULA

a(n) = (2 * A007185(n) - 1) mod 10^n.

PROG

(Sage) def A224473(n) : return crt(1, -1, 2^n, 5^n);

CROSSREFS

Cf. A033819. Corresponding 10-adic number is A091661. The other trimorphic numbers ending in 9 are included in A002283, A198971 and A224475.

Sequence in context: A228018 A081655 A181539 * A146798 A055428 A359186

Adjacent sequences: A224470 A224471 A224472 * A224474 A224475 A224476

KEYWORD

nonn,base

AUTHOR

Eric M. Schmidt, Apr 07 2013

STATUS

approved