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A105814 a(n) = n^2 + (n concatenated with n). 0

%I

%S 12,26,42,60,80,102,126,152,180,1110,1232,1356,1482,1610,1740,1872,

%T 2006,2142,2280,2420,2562,2706,2852,3000,3150,3302,3456,3612,3770,

%U 3930,4092,4256,4422,4590,4760,4932,5106,5282,5460,5640,5822,6006,6192,6380,6570

%N a(n) = n^2 + (n concatenated with n).

%F a(n) = n^2 + n*(1+10^(1+floor(log_10(n)))). - _Robert Israel_, Jul 30 2015

%F a(n) = n^2 + A020338(n). - _Michel Marcus_, Jul 31 2015

%e 1 + 11 = 12, 4 + 22 = 26, 9 + 33 = 42, 16 + 44 = 60, ..., 100 + 1010 = 1110.

%p seq(n^2 + n*(1+10^(1+ilog10(n))),n=1..100); # _Robert Israel_, Jul 30 2015

%t f[n_] := Block[{id = IntegerDigits[n]}, n^2 + FromDigits[ Join[id, id]]]; Table[ f[n], {n, 45}] (* _Robert G. Wilson v_, May 10 2005 *)

%o (PARI) vector(50, n, n^2 + eval(Str(n,n))) \\ _Michel Marcus_, Jul 31 2015

%o (MAGMA) [Seqint(Intseq(n) cat Intseq(n))+n^2: n in [1..50]] /* or */ [n^2+n*(1+10^(1+Floor(Log(n)/Log(10)))): n in [1..50]]; // _Vincenzo Librandi_, Jul 31 2015

%K base,easy,nonn

%O 1,1

%A _Eric Angelini_, May 05 2005

%E More terms from _Robert G. Wilson v_, May 10 2005

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Last modified August 15 12:49 EDT 2020. Contains 336500 sequences. (Running on oeis4.)