

A161999


For n even a(n) = a(n1) + 10*a(n2), for n odd a(n) = a(n3) + 10 a(n2); with a(1) = 0, a(2) = 1.


2



0, 1, 1, 10, 20, 101, 301, 1030, 4040, 10601, 51001, 110050, 620060, 1151501, 7352101, 12135070, 85656080, 128702801, 985263601, 1372684090, 11225320100, 14712104501, 126965305501, 158346365110, 1427999420120
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OFFSET

1,4


LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (0, 20, 0, 99).


FORMULA

a(n)=20*a(n2)99*a(n4). G.f.: x^2*(1x+10*x^2)/((3*x1)*(3*x+1)*(11*x^21)). [From R. J. Mathar, Jul 13 2009]


EXAMPLE

As pairs:
0, 1
1, 10
20, 101
301, 1030
4040, 10601
51001, 110050
620060, 1151501
7352101, 12135070
85656080, 128702801


MATHEMATICA

nxt[{n_, a_, b_, c_}]:={n+1, b, c, If[OddQ[n], c+10b, a+10b]}; NestList[nxt, {2, 0, 1, 1}, 30][[All, 2]] (* or *) LinearRecurrence[{0, 20, 0, 99}, {0, 1, 1, 10}, 30] (* Harvey P. Dale, May 03 2018 *)


CROSSREFS

Combination of A081192 and A016190. Triangle A007318 (even /uneven rows). Partly same function as A015446. A001020 (as sum of pairs of 2n).A001019 (as difference of pairs of 2n)
Cf. A162849.
Sequence in context: A166641 A101244 A260743 * A086069 A220012 A154330
Adjacent sequences: A161996 A161997 A161998 * A162000 A162001 A162002


KEYWORD

nonn,less


AUTHOR

Mark Dols, Jun 24 2009, Jun 28 2009, Jul 13 2009


EXTENSIONS

Edited by N. J. A. Sloane, Jun 30 2009
NAME adapted to offset.  R. J. Mathar, Jun 19 2021


STATUS

approved



