A037701 - OEIS

A037701

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

1, 12, 123, 1230, 12301, 123012, 1230123, 12301230, 123012301, 1230123012, 12301230123, 123012301230, 1230123012301, 12301230123012, 123012301230123, 1230123012301230, 12301230123012301, 123012301230123012, 1230123012301230123, 12301230123012301230

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OFFSET

1,2

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(0)=1, a(1)=12, a(2)=123, a(3)=1230, a(4)=12301, a(n) = 10*a(n-1) + a(n-4) - 10*a(n-5). - Harvey P. Dale, Jun 07 2011

G.f.: x*(1+2*x+3*x^2) / ( (x-1)*(10*x-1)*(1+x)*(x^2+1) ). - R. J. Mathar, Aug 12 2013

MATHEMATICA

Rest[RecurrenceTable[{a[0]==0, a[n]==10a[n-1]+Mod[n, 4]}, a[n], {n, 20}]] (* or *) LinearRecurrence[{10, 0, 0, 1, -10}, {1, 12, 123, 1230, 12301}, 20] (* Harvey P. Dale, Jun 07 2011 *)

PROG

(PARI) Vec(x*(1+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: A079847 A144165 A113572 * A037610 A035239 A344183

Adjacent sequences: A037698 A037699 A037700 * A037702 A037703 A037704

KEYWORD

nonn,base,easy

AUTHOR

Clark Kimberling

EXTENSIONS

More terms from Harvey P. Dale, Jun 07 2011

STATUS

approved