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A224473 (2*5^(2^n) - 1) mod 10^n: a sequence of trimorphic numbers ending in 9. 9
9, 49, 249, 1249, 81249, 781249, 5781249, 25781249, 425781249, 6425781249, 36425781249, 836425781249, 9836425781249, 19836425781249, 519836425781249, 2519836425781249, 12519836425781249, 512519836425781249, 4512519836425781249, 84512519836425781249 (list; graph; refs; listen; history; text; internal format)
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 Weisstein's World of Mathematics, Trimorphic Number
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
KEYWORD
nonn,base
AUTHOR
Eric M. Schmidt, Apr 07 2013
STATUS
approved

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Last modified February 25 09:10 EST 2024. Contains 370313 sequences. (Running on oeis4.)