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a(n) = 1001*n.
1

%I #25 Sep 08 2022 08:45:40

%S 1001,2002,3003,4004,5005,6006,7007,8008,9009,10010,11011,12012,13013,

%T 14014,15015,16016,17017,18018,19019,20020,21021,22022,23023,24024,

%U 25025,26026,27027,28028,29029,30030,31031,32032,33033,34034,35035,36036,37037,38038

%N a(n) = 1001*n.

%C Previous name was: 143*7n.

%C Property of 143*7n shown by Ghersi (see References):

%C a(n) = n00n for n from 1 to 9;

%C a(n) = n0n for n from 10 to 99;

%C a(n) = nn for n from 100 to 999.

%D I. Ghersi, Matematica dilettevole e curiosa, Hoepli (1967), p. 138

%H Vincenzo Librandi, <a href="/A153814/b153814.txt">Table of n, a(n) for n = 1..1000</a>

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).

%F G.f.: 1001*x/(1-x)^2. - _Vincenzo Librandi_, Feb 26 2012 [corrected by _Georg Fischer_, May 10 2019]

%F a(n) = 2*a(n-1) - a(n-2). - _Vincenzo Librandi_, Feb 26 2012

%t Table[1001 n, {n, 1, 40}] (* _Bruno Berselli_, Mar 30 2016 *)

%o (PARI) for(n=1, 40, print1(1001*n", ")); \\ _Vincenzo Librandi_, Feb 26 2012

%o (Magma) [1001*n: n in [1..40]]; // _Bruno Berselli_, Mar 30 2016

%Y Cf. A018768.

%K nonn,easy

%O 1,1

%A _Vincenzo Librandi_, Jan 02 2009

%E Name changed by _Michel Marcus_, Mar 30 2016