A037743 - OEIS

A037743

Decimal expansion of a(n) is given by the first n terms of the periodic sequence with initial period 2,1,3,0.

2, 21, 213, 2130, 21302, 213021, 2130213, 21302130, 213021302, 2130213021, 21302130213, 213021302130, 2130213021302, 21302130213021, 213021302130213, 2130213021302130, 21302130213021302, 213021302130213021, 2130213021302130213, 21302130213021302130

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..20.

Index entries for linear recurrences with constant coefficients, signature (10,0,0,1,-10).

FORMULA

a(n) = 10*a(n-1) + a(n-4) - 10*a(n-5). G.f.: x*(2+x+3*x^2) / ((x-1)*(10*x-1)*(1+x)*(x^2+1)). - R. J. Mathar, Oct 05 2009

MATHEMATICA

Table[FromDigits[PadRight[{}, n, {2, 1, 3, 0}]], {n, 20}] (* Harvey P. Dale, Feb 24 2025 *)

PROG

(PARI) Vec(x*(2+x+3*x^2)/((x-1)*(10*x-1)*(1+x)*(x^2+1)) + O(x^25)) \\ Jinyuan Wang, Apr 14 2020

CROSSREFS

Sequence in context: A037575 A305659 A008351 * A037638 A131698 A163068

Adjacent sequences: A037740 A037741 A037742 * A037744 A037745 A037746

KEYWORD

nonn,base,easy,changed

AUTHOR

Clark Kimberling

EXTENSIONS

More terms from Harvey P. Dale, Aug 16 2011

STATUS

approved