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A084054
5*n digit-reversed mod 5.
6
1, 1, 2, 2, 3, 3, 4, 4, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 0, 0, 0, 0, 0, 0, 0
OFFSET
2,3
COMMENTS
The pattern of increasing frequency of repetition of digits is clear.
FORMULA
Contribution from Enrique Pérez Herrero, Jun 14 2010: (Start)
a(n)=mod(floor(5*n/10^(floor(log_10(5*n)))),5), this formula comes from the modulus 5 of the first digit of 5*n.
a(10^n)=1
(End)
EXAMPLE
a(61) =3 as, 61*5 = 305,digit reversed = 503 ==3 (mod 5)
MATHEMATICA
Contribution from Enrique Pérez Herrero, Jun 14 2010: (Start)
A084054[n_Integer]:=Mod[FromDigits[Reverse[IntegerDigits[5*n]]], 5];
(* Alternative formula *)
A084054[n_Integer]:=Mod[Floor[5*n/10^Floor[Log[10, 5*n]]], 5] (End)
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), May 26 2003
EXTENSIONS
More terms from Ray Chandler, May 27 2003
STATUS
approved