A332149 - OEIS

A332149

a(n) = 4*(10^(2*n+1)-1)/9 + 5*10^n.

9, 494, 44944, 4449444, 444494444, 44444944444, 4444449444444, 444444494444444, 44444444944444444, 4444444449444444444, 444444444494444444444, 44444444444944444444444, 4444444444449444444444444, 444444444444494444444444444, 44444444444444944444444444444, 4444444444444449444444444444444

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OFFSET

0,1

LINKS

Table of n, a(n) for n=0..15.

Index entries for linear recurrences with constant coefficients, signature (111,-1110,1000).

FORMULA

a(n) = 4*A138148(n) + 9*10^n = A002278(2n+1) + 5*10^n.

G.f.: (9 - 505*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

A332149 := n -> 4*(10^(2*n+1)-1)/9+5*10^n;

MATHEMATICA

Array[4 (10^(2 # + 1)-1)/9 + 5*10^# &, 15, 0]

PROG

(PARI) apply( {A332149(n)=10^(n*2+1)\9*4+5*10^n}, [0..15])

(Python) def A332149(n): return 10**(n*2+1)//9*4+5*10**n

CROSSREFS

Cf. A002275 (repunits R_n = (10^n-1)/9), A002278 (4*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. A332140 .. A332148 (variants with different middle digit 0, ..., 8).

Sequence in context: A157595 A042415 A277360 * A112910 A180585 A102909

Adjacent sequences: A332146 A332147 A332148 * A332150 A332151 A332152

KEYWORD

nonn,base,easy

AUTHOR

M. F. Hasler, Feb 09 2020

STATUS

approved