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A332159 a(n) = 5*(10^(2*n+1)-1)/9 + 4*10^n. 9
9, 595, 55955, 5559555, 555595555, 55555955555, 5555559555555, 555555595555555, 55555555955555555, 5555555559555555555, 555555555595555555555, 55555555555955555555555, 5555555555559555555555555, 555555555555595555555555555, 55555555555555955555555555555, 5555555555555559555555555555555 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
LINKS
FORMULA
a(n) = 5*A138148(n) + 9*10^n = A002279(2n+1) + 4*10^n.
G.f.: (9 - 404*x - 100*x^2)/((1 - x)(1 - 10*x)(1 - 100*x)).
a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3) for n > 2.
MAPLE
A332159 := n -> 5*(10^(2*n+1)-1)/9+4*10^n;
MATHEMATICA
Array[5 (10^(2 # + 1)-1)/9 + 4*10^# &, 15, 0]
Table[FromDigits[Join[PadRight[{}, n, 5], PadRight[{9}, n+1, 5]]], {n, 0, 20}] (* or *) LinearRecurrence[ {111, -1110, 1000}, {9, 595, 55955}, 20] (* Harvey P. Dale, May 31 2023 *)
PROG
(PARI) apply( {A332159(n)=10^(n*2+1)\9*5+4*10^n}, [0..15])
(Python) def A332159(n): return 10**(n*2+1)//9*5+4*10**n
CROSSREFS
Cf. A002275 (repunits R_n = (10^n-1)/9), A002279 (5*R_n), A011557 (10^n).
Cf. A138148 (cyclops numbers with binary digits), A002113 (palindromes).
Cf. A332119 .. A332189 (variants with different repeated digit 1, ..., 8).
Cf. A332150 .. A332159 (variants with different middle digit 0, ..., 9).
Sequence in context: A061611 A238609 A015092 * A139107 A226552 A277232
KEYWORD
nonn,base,easy
AUTHOR
M. F. Hasler, Feb 09 2020
STATUS
approved

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Last modified May 20 19:00 EDT 2024. Contains 372720 sequences. (Running on oeis4.)