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A205085 a(n) = n 5's sandwiched between two 1's. 1
11, 151, 1551, 15551, 155551, 1555551, 15555551, 155555551, 1555555551, 15555555551, 155555555551, 1555555555551, 15555555555551, 155555555555551, 1555555555555551, 15555555555555551, 155555555555555551, 1555555555555555551, 15555555555555555551 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
LINKS
FORMULA
a(0)=11, a(n) = 10*a(n-1) + 41.
a(n) = (140*10^n - 41)/9 (see PARI code by Charles R Greathouse IV).
a(n) = 11*a(n-1) - 10*a(n-2). - Vincenzo Librandi, Jan 23 2012
MATHEMATICA
a[0]=11; a[n_]:=a[n-1]*10+41; Table[a[n], {n, 0, 44}]
LinearRecurrence[{11, -10}, {11, 151}, 50] (* Vincenzo Librandi, Jan 23 2012 *)
Table[10FromDigits[PadRight[{1}, n, 5]]+1, {n, 20}] (* Harvey P. Dale, May 02 2019 *)
PROG
(PARI) a(n)=(140*10^n-41)/9 \\ Charles R Greathouse IV, Jan 23 2012
(Magma) I:=[11, 151]; [n le 2 select I[n] else 11*Self(n-1)-10*Self(n-2): n in [1..25]]; // Vincenzo Librandi, Jan 23 2012
CROSSREFS
Sequence in context: A038141 A307072 A142083 * A068646 A176365 A077577
KEYWORD
nonn,base,easy,less
AUTHOR
STATUS
approved

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Last modified April 12 22:48 EDT 2024. Contains 371639 sequences. (Running on oeis4.)