A205087 - OEIS

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A205087

a(n)=n 7's sandwiched between two 1's.

11, 171, 1771, 17771, 177771, 1777771, 17777771, 177777771, 1777777771, 17777777771, 177777777771, 1777777777771, 17777777777771, 177777777777771, 1777777777777771, 17777777777777771, 177777777777777771, 1777777777777777771, 17777777777777777771

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OFFSET

0,1

LINKS

Table of n, a(n) for n=0..18.

Index entries for linear recurrences with constant coefficients, signature (11,-10).

FORMULA

a(0)=1, a(n) = 10*a(n-1)+61.

a(n) = (160*10^n-61)/9 (see PARI's code by Charles R Greathouse IV).

MATHEMATICA

a[0]=11; a[n_]:=a[n-1]*10+61; Table[a[n], {n, 0, 44}]

Table[10 FromDigits[PadRight[{1}, n, 7]]+1, {n, 20}] (* Harvey P. Dale, Nov 18 2022 *)

PROG

(PARI) a(n)=(160*10^n-61)/9 \\ Charles R Greathouse IV, Jan 23 2012

CROSSREFS

Sequence in context: A233290 A167245 A331929 * A064182 A139792 A025758

Adjacent sequences: A205084 A205085 A205086 * A205088 A205089 A205090

KEYWORD

nonn,easy,less,base

AUTHOR

José María Grau Ribas, Jan 22 2012

STATUS

approved