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%I #6 Mar 11 2018 18:50:32
%S 1,13,147,1593,16161,173951,1852963,19753197,109876543,1111111111,
%T 12345678901,135791357913,1470369258147,15937159371593,
%U 161616161616161,1739517395173951,18529630741852963,197531975319753197
%N Form triangle shown below, in which the n-th row contains n terms of an arithmetic progression with first term 1 and common difference n. Then a(n) = terms of the n-th row (mod 10), concatenated.
%H Harvey P. Dale, <a href="/A110748/b110748.txt">Table of n, a(n) for n = 1..1000</a>
%e 1
%e 1 3
%e 1 4 7
%e 1 5 9 13
%e 1 6 11 16 21
%e ...
%t Table[FromDigits[Mod[Range[1,n^2-n+1,n],10]],{n,20}] (* _Harvey P. Dale_, Mar 11 2018 *)
%K base,nonn
%O 1,2
%A _Amarnath Murthy_, Aug 10 2005
%E More terms from Melissa Ciacchi (mciacchi(AT)ashland.edu), Feb 28 2006