A100846 Concatenate (1,n,n,1).
1001, 1111, 1221, 1331, 1441, 1551, 1661, 1771, 1881, 1991, 110101, 111111, 112121, 113131, 114141, 115151, 116161, 117171, 118181, 119191, 120201, 121211, 122221, 123231, 124241, 125251, 126261, 127271, 128281, 129291, 130301, 131311, 132321
Offset: 0
Examples
For n = 0, concatenate(1,n,n,1) is 1001 = a(0). For n = 5, concatenate(1,n,n,1) is 1551 = a(5). For n = 10, concatenate(1,n,n,1) is 110101 = a(10).
Links
- M. F. Hasler, Table of n, a(n) for n = 0..10000 (Terms a(1..9999) from Robert Israel)
Crossrefs
Programs
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Maple
seq(seq((10^(2*d+1)+1+(10^(d+1)+10)*n), n=`if`(d>1,10^(d-1),0) .. 10^d-1),d=1..3); # Robert Israel, Dec 30 2015, edited for n=0 by M. F. Hasler, Jun 25 2018
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Mathematica
For[n = 0, n < 30, n++, l := Floor[Log[10, Min[n,1]] + 1]; gvout := (n*10^l + n)*10 + 1; m := Floor[Log[10, gvout]]; giveout := 10^(m + 1) + out; Print[giveout]] (* Stefan Steinerberger, Jan 27 2006, edited for n=0 by M. F. Hasler, Jun 25 2018 *)
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PARI
A100846(n)=eval(Str(1,n,n,1)) \\ M. F. Hasler, Jun 22 2018
Formula
G.f.: 1001 + x*(31-11*x)/(1-x)^2 + Sum_{k>=0} 90*(12*10^(2*k)*(1-x)+10^k*x)*x^(10^k)/(1-x)^2. - Robert Israel, Dec 30 2015
Extensions
More terms from Stefan Steinerberger, Jan 27 2006
Definition reworded and missing 1001 added by M. F. Hasler, Jun 22 2018