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%I #15 Oct 02 2020 07:23:38
%S 1,2,1,2,3,1,2,3,4,5,1,2,3,4,5,6,7,1,2,3,4,5,6,7,8,9,10,11,1,2,3,4,5,
%T 6,7,8,9,10,11,12,13,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,1,2,3,
%U 4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,1,2,3,4,5,6,7,8,9
%N Irregular triangle: row n is 1, 2, 3, 4, .., prime(n).
%e From _Omar E. Pol_, May 29 2012: (Start)
%e Written as an irregular triangle the sequence begins:
%e 1, 2;
%e 1, 2, 3;
%e 1, 2, 3, 4, 5;
%e 1, 2, 3, 4, 5, 6, 7;
%e 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11;
%e 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13;
%e Row n has length A000040(n). (End)
%t Flatten@Range@Prime@Range[9] (* _Arkadiusz Wesolowski_, Jul 02 2012 *)
%Y Cf. A002260.
%K nonn,easy,tabf
%O 1,2
%A Vasiliy Danilov (danilovv(AT)usa.net), Jun 15 1998
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